obesity

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Definition

Obesity is an abnormal accumulation of body fat, usually 20% or more over an individual's ideal body weight. Obesity is associated with increased risk of illness, disability, and death.

Description

Obesity traditionally has been defined as a weight at least 20% above the weight corresponding to the lowest death rate for individuals of a specific height, gender, and age (ideal weight). Twenty to forty percent over ideal weight is considered mildly obese; 40–100% over ideal weight is considered moderately obese; and 100% over ideal weight is considered severely, or morbidly, obese. More recent guidelines for obesity use a measurment called BMI (body mass index) which is the individual's weight multiplied by 703 and then divided by twice the height in inches. BMI of 25.9–29 is considered overweight; BMI over 30 is considered obese. Measurements and comparisons of waist and hip circumference can also provide some information regarding risk factors associated with weight. The higher the ratio, the greater the chance for weight-associated complications. Calipers can be used to measure skin-fold thickness to determine whether tissue is muscle (lean) or adipose tissue (fat).

Much concern has been generated about the increasing incidence of obesity among Americans. Some studies have noted an increase from 12% to 18% occurring between 1991 and 1998. Other studies have actually estimated that a full 50% of all Americans are overweight. The World Health Organization terms obesity a worldwide epidemic, and the diseases which can occur due to obesity are becoming increasingly prevalent.

Excessive weight can result in many serious, potentially life-threatening health problems, including hypertension, Type II diabetes mellitus (non-insulin dependent diabetes), increased risk for coronary disease, increased unexplained heart attack, hyperlipidemia, infertility, and a higher prevalence of colon, prostate, endometrial, and, possibly, breast cancer. Approximately 300, 000 deaths a year are attributed to obesity, prompting leaders in public health, such as former Surgeon General C. Everett Koop, M.D., to label obesity "the second leading cause of preventable deaths in the United States."

— Rosalyn Carson-DeWitt

Dictionary: o·be·si·ty   (ō-bē'sĭ-tē)

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The condition of being obese; increased body weight caused by excessive accumulation of fat.

The presence of excess body fat. The great prevalence of this condition, its severe consequences for physical and mental health, and the difficulty of treating it make the prevention of obesity a major public health priority.

Obesity is most often defined in terms of body weight relative to height, since both height and weight are easily measured. Obesity is considered to begin at a weight-for-height that is 20–30% above desirable weight, with this desirable weight taken as the midpoint of ranges of weight associated with the greatest longevity in studies of life-insured individuals. In population surveys, obesity is defined as a body weight that meets or exceeds the 85th percentile of the Body Mass Index (BMI), an index of weight-for-height that correlates well with body fat content. See also Adipose tissue.

The prevalence of obesity increases with age, is higher in women than men, and is highest among the poor and minority groups. Obesity increases the likelihood of high blood cholesterol, high blood pressure, and diabetes, and therefore of the diseases for which such conditions are risk factors—coronary heart disease, stroke, and kidney disease. It also increases the likelihood of gallbladder disease and cancers of the breast and uterus. Thus, obesity increases overall mortality rates, and it does so in proportion to the degree and duration of overweight. Individuals who become obese at the earliest ages are at highest risk of premature mortality. Distribution of excess fat to the upper body rather than the lower body may also increase risk.

The causes of most cases of obesity are poorly understood. At the simplest level, obesity results from an excess of energy (caloric) intake over expenditure, but this statement does not explain why some individuals can eat as much as they like without gaining weight while others remain overweight despite constant dieting. Studies of genetically obese animals and those with damage to the part of the brain called the hypothalamus suggest that individuals may balance body weight around a “setpoint” that is maintained—without conscious control—by variations in metabolic rate in response to caloric intake. Variations in the prevalence of obesity among population groups suggest a genetic basis for the condition. The complexity of body-weight regulatory mechanisms suggests that obesity is not due to a single cause but, like other chronic diseases, is multifactorial in origin. Specific inherited differences that might influence setpoints include differences in nearly every anatomic, neurologic, and biochemical factor known to affect food intake and utilization, energy metabolism, and energy expenditure. See also Energy metabolism; Metabolic disorders.

Because the causes of obesity are incompletely understood, it is difficult to formulate effective treatment strategies. Studies suggest that programs combining diet and exercise help obese individuals lose more weight and maintain losses longer than either program does separately. See also Food; Nutrition.

Obesity is most commonly defined as a condition of weighing at least 20% over ideal body weight, where ideal body weight is determined in the US by the 1959 or 1983 Metropolitan Life Insurance Company Tables. Like many aspects of obesity, use of life insurance tables as the sole indicator remains controversial. These insurance charts do not take into account the changes in ideal weight with age or provide information on body fat distribution; nor do they base measurements on all ethnic groups and those of the lower socioeconomic classes. To counter such biases, obesity can be determined by body mass index (which relates weight to height) and the percentage of body fat.

The causes of obesity continue to be debated and studied. Though it has long been considered the simple result of too little exercise and too much eating, new research suggests there may also be some hereditary influence, and particularly that the genetic tendency for obesity may be correlated to the mother's weight. Relatively unusual causes include adult-onset diabetes, deficient thyroid hormone secretion, and, very rarely, tumours of the adrenal gland, pancreas, or pituitary gland. Unexplained abnormal function of the brain's appetite control centre may also play a role. Researchers are particularly concerned about the increasing number of children and adolescents who are overweight in the US and Europe.

Obesity may cause a variety of health complications. Most clearly, overweight has an adverse effect on life expectancy. In general, the greater the degree of overweight, the higher the mortality or excess death rate. Obesity may be associated with elevated blood cholesterol, and has been linked to hypertension, diabetes, cancer, coronary artery heart disease, degenerative arthritis, gall stones, sleep disorders, and depression.

For many the ‘psychological burden’ of being obese in Western cultures, which prize slenderness, particularly in women, is an additional adverse effect. Prior to the nineteenth century, overweight and fatness stood as a sign of health and prosperity, and conveyed social esteem. By the mid and late nineteenth century, a new ethos emerged which championed slenderness as a sign of both beauty and physical health. By the early twentieth century, on the other hand, obesity became associated with laziness, gluttony, and the lower classes. As Keith Walden has written, ‘females who stayed slim demonstrated that they had the money and sense to buy nutritious foods and eat balanced meals, and that they had the time to exercise. They did not have menial jobs which required substantial brawn to perform.’ In twenty-first-century Western culture, especially for whites, and the middle and upper classes, the abhorrence of fat and obesity continues. As Anne Beller describes it, fat is suicidal: a sin at best and at worst a sort of felony. Yet for many African Americans and Hispanics, as well as other ethnic groups, a larger body still holds positive social value.

Suggested treatments for obesity range from a plethora of rarely successful fad diets to medical procedures such as stapling the stomach to reduce intake or shortening the intestines to curtail absorption. The most tried and true method remains adjustment of the energy balance — decreasing caloric intake while increasing energy usage. Vigorous exercise not only ‘burns’ nutrient stores but is also shown in some situations to increase metabolic rate for up to 15 hours after activity. Those with a hereditary tendency toward obesity find it more difficult to lose weight, due to a lower resting metabolic rate and possible complications in appetite regulation. In this regard, and in evolutionary terms, a tendency toward obesity can actually have survival value — a lower metabolic rate and a substantial fat store would allow one to live longer in times of famine. But in the contemporary West, where food is relatively plentiful and slenderness highly prized, it works to one's disadvantage.

— Margaret A. Lowe

Bibliography

• Beller, A. S. Fat and thin: a natural history of obesity. Farrar, Straus and Giroux, New York.
• Walden, K. (1985). The road to Fat City: an interpretation of the development of weight consciousness in Western society. Historical reflections, 12, 331-73

See also body composition; dieting; energy balance; weight.

Excessive accumulation of body fat. A body mass index above 30 is considered to be obesity (and above 40 gross obesity). The desirable range of BMI for optimum life expectancy is 20-25; between 25 and 30 is considered to be overweight rather than obesity. People more than 50% above desirable weight are twice as likely to die prematurely as those within the desirable weight range.

Obesity is due to the excessive storage of fat in the body, particularly under the skin and around certain internal organs. In 1985, 34 million Americans were obese. Of British adults surveyed in 1991, 13 per cent of men and 15 per cent of women were obese; double the percentage of people who were obese in 1981. A 1995 survey indicates that these figures are continuing to rise. Obesity can be caused by diseases, such as certain cancers, gall-bladder diseases, and hormonal imbalances, but these causes are rare. Many obese people suggest that their condition is due to underactive thyroid glands, but this accounts for less than one in a thousand cases. Most obesity results from eating too much and not exercising enough. This results in a positive energy balance, more energy is consumed than expended. For every 3500 Calories consumed above requirements, approximately one pound of fat is stored in the body.

Obesity is difficult to define quantitatively without knowing how much fat is normal for a given person. Nevertheless, it is generally agreed that the proportion of fat in the body should not exceed 20-25 per cent in men and 28-30 per cent in women. Many medical authorities use body mass as an indicator (see body mass index); people with a body mass index exceeding 30 are considered obese. However, obesity is not the same as being overweight. A very muscular person may be heavy but still have a very low fat content. Heavy body-builders often have less than 10 per cent body fat. There are two main types of obesity: childhood onset obesity and adult onset obesity.

Childhood onset obesity may develop because of hormonal imbalances or some other illness, but it is usually caused by overeating when young. This results in the production of an abnormally high number of adipocytes, cells specialized for fat storage. Adults who were obese as children tend to retain a high number of adipocytes, even if they are thin and have a low fat diet. The high number of adipocytes means that a large storage space is always available for fat. Thus adults who suffered childhood onset obesity are generally predisposed to obesity.

Adult onset obesity occurs when a person becomes obese for the first time after reaching adulthood. He or she usually has a normal number of adipocytes but each one is enlarged with fat. Slimming leads to the fat cells returning to normal size. Adults who have suffered adult onset obesity usually find it much easier to control their weight than adults who were obese as children.

Obesity is a major health hazard. Obese people are predisposed to a number of diseases, including diabetes, high blood pressure, and cardiovascular diseases. Some medical experts suggest that life expectancy decreases by approximately 1 per cent for each pound of excess fat carried by an individual between the ages of 45 and 50.

A bodily condition marked by excessive generalized deposition and storage of fat.

Definition

Obesity is an abnormal accumulation of body fat, usually 20% or more over an individual's ideal body weight. Obesity is associated with increased risk of illness, disability, and death.

The branch of medicine that deals with the study and treatment of obesity is known as bariatrics. As obesity has become a major health problem in the United States, bariatrics has become a separate medical and surgical specialty.

Description

Obesity traditionally has been defined as body weight at least 20% above the weight corresponding to the lowest death rate for individuals of a specific height, sex, and age (designated as the ideal weight). Twenty to forty percent over ideal weight is considered mildly obese; 40–100% over ideal weight is considered moderately obese; and 100% over ideal weight is considered severely, or morbidly, obese. According to some estimates, approximately 25% of the United States population can be considered obese, 4 million of whom are morbidly obese. Other studies state that over 50% of American adults are obese, based on body mass index (BMI) measurements. Excessive weight can result in many serious, and potentially deadly, health problems, including hypertension, Type II diabetes mellitus (non-insulin dependent diabetes), increased risk for coronary disease, increased unexplained heart attack, hyperlipidemia, infertility, and a higher prevalence of colon, prostate, endometrial, and possibly, breast cancer. Approximately 300,000 deaths a year are attributed to obesity, prompting leaders in public health, such as former Surgeon General C. Everett Koop to label obesity "the second leading cause of preventable deaths in the United States."

Causes & Symptoms

The mechanism for excessive weight gain is clear—more calories are consumed than the body burns, and the excess calories are stored as fat (adipose) tissue. However, the exact cause is not as clear and likely arises from a complex combination of factors. Genetic factors significantly influence how the body regulates appetite and the rate at which it turns food into energy (metabolic rate). Studies of adoptees confirm this relationship. The majority of adoptees followed a pattern of weight gain that more closely resembled that of their birth parents than their adoptive parents. A genetic predisposition to weight gain, however, does not automatically mean that a person will be obese. Eating habits and patterns of physical activity also play a significant role in the amount of weight a person gains.

Some recent studies have indicated that the amount of fat in a person's diet may have a greater impact on weight than the number of calories the food contains. Carbohydrates like cereals, breads, fruits and vegetables, and protein (fish, lean meat, turkey breast, skim milk) are converted to fuel almost as soon as they are consumed. Most fat calories are immediately stored in fat cells, which add to the body's weight and girth as they expand and multiply. There is continuing research on the theory that fat is metabolized as fuel and energy and that only excess carbohydrates are converted to stored fat. Current evidence shows that weight gain comes mostly from total calories consumed, rather than from the amount of carbohydrates. A study published in 2002 found that low-fat diets are no more effective in weight reduction programs than low-calorie diets. At any rate, a sedentary life-style, particularly prevalent in affluent societies like the United States, can contribute to weight gain. Psychological factors, such as depression and low self-esteem may, in some cases, also play a role in weight gain.

At what stage of life a person becomes obese can effect his or her ability to lose weight. In childhood, excess calories are converted into new fat cells (hyperplastic obesity), while excess calories consumed in adulthood only serve to expand existing fat cells (hypertrophic obesity). Since dieting and exercise can only reduce the size of fat cells, not eliminate them, persons who were obese as children can have great difficulty losing weight, since they may have up to five times as many fat cells as someone who became overweight as an adult.

Obesity can also be a side effect of certain disorders and conditions, including:

• Cushing's syndrome, a disorder involving the excessive release of the hormone cortisol

• hypothyroidism, a condition caused by an underactive thyroid gland
• neurologic disturbances, such as damage to the hypothalamus, a structure located deep within the brain that helps regulate appetite
• consumption of certain drugs, such as steroids, antipsychotic medications, or antidepressants

The major symptoms of obesity are excessive weight gain and the presence of large amounts of fatty tissue. Obesity can also give rise to several secondary conditions, including:

• arthritis and other orthopedic problems, such as lower back pain
• heartburn
• high cholesterol levels
• high blood pressure
• menstrual irregularities or cessation of menstruation (amenorhhea)
• shortness of breath that can be incapacitating
• skin disorders, arising from the bacterial breakdown of sweat and cellular material in thick folds of skin or from increased friction between folds

Diagnosis

Dignosis of obesity is made by observation and by comparing the patient's weight to ideal weight charts. Many doctors and obesity researchers refer to the body mass index (BMI), which uses a height-weight relationship to calculate an individual's ideal weight and personal risk of developing obesity-related health problems. Physicians may also obtain direct measurements of an individual's body fat content by using calipers to measure skin-fold thickness at the back of the upper arm and other sites. The most accurate means of measuring body fat content involves immersing a person in water and measuring relative displacement; however, this method is very impractical and is usually only used in scientific studies requiring very specific assessments. Women whose body fat exceeds 30% and men whose body fat exceeds 25% are generally considered obese.

Doctors may also note how a person carries excess weight on his or her body. Studies have shown that this factor may indicate whether or not an individual has a predisposition to develop certain diseases or conditions that may accompany obesity. "Apple-shaped" individuals who store most of their weight around the waist and abdomen are at greater risk for cancer, heart disease, stroke, and diabetes than "pear-shaped" people whose extra pounds settle primarily in their hips and thighs.

Treatment

Treatment of obesity depends primarily on the degree of a person's overweight and his or her overall health. However, to be successful, any treatment must affect life-long behavioral changes rather than short-term weight loss. "Yo-yo" dieting, in which weight is repeatedly lost and regained, has been shown to increase a person's likelihood of developing fatal health problems than if the weight had been lost gradually or not lost at all. Behavior-focused treatment should concentrate on:

• What a person eats and how much. This aspect may involve keeping a food diary and developing a better understanding of the nutritional value and fat content of foods. It may also involve changing grocery shopping habits (e.g. buying only what is on a prepared list and going only on a certain day), timing of meals (to prevent feelings of hunger, a person may plan frequent small meals), and actually slowing down the rate at which a person eats.
• How a person responds to food. This may involve understanding what psychological issues underlie a person's eating habits. For example, one person may binge eat when under stress, while another may always use food as a reward. In recognizing these psychological triggers, an individual can develop alternate coping mechanisms that do not focus on food.
• How people spend their time. Making activity and exercise an integral part of everyday life is a key to achieving and maintaining weight loss. Starting slowly and building endurance keeps individuals from becoming discouraged. Varying routines and trying new activities also keeps interest high.

For most who are mildly obese, these behavior modifications entail lifestyle changes they can make independently while being supervised by a family physician. Other mildly obese persons may seek the help of a commercial weight loss program (e.g. Weight Watchers). The effectiveness of these programs is difficult to assess, since programs vary widely, dropout rates are high, and few employ members of the medical community. However, programs that emphasize realistic goals, gradual progress, sensible eating, and exercise can be very helpful and are recommended by many doctors. Programs that promise instant weight loss or feature severely restricted diets are not effective and, in some cases, can be dangerous.

For individuals who are moderately obese, medically supervised behavior modification and weight loss are required. While doctors will put most moderately obese patients on a balanced low-calorie diet (1200–1500 calories a day), they may recommend that certain individuals follow a very low-calorie liquid protein diet (400–700 calories) for as long as three months. This therapy, however, should not be confused with commercial liquid-protein diets or commercial weight-loss shakes and drinks. Doctors tailor these diets to specific patients, monitor patients carefully, and use them for only a short period of time. In addition to reducing the amount and type of calories consumed by the patient, doctors will recommend professional therapists or psychiatrists who can help the individual effectively change his or her behavior in regard to eating.

The Chinese herb ephedra (Ephedra sinica, or ma huang), combined with exercise and a low-fat diet in physician-supervised weight-loss programs, can cause at least a temporary increase in weight loss. However, the large doses of ephedra required to achieve the desired result can also cause:

• anxiety
• heart arrhythmias
• heart attack
• high blood pressure
• insomnia
• irritability
• nervousness
• seizures
• strokes
• death

Ephedra should not be used by anyone with a history of diabetes, heart disease, or thyroid problems. It is not recommended for long-term use, and can cause serious medical or psychiatric problems if used too long. An article that appeared in the Journal of the American Medical Association in early 2003 advised against the use of ephedra.

Diuretic herbs, which increase urine production, can cause short-term weight loss but cannot help patients achieve lasting weight control. The body responds to heightened urine output by increasing thirst to replace lost fluids, and patients who use diuretics for an extended period of time eventually start retaining water again anyway. In moderate doses, psyllium, a mucilaginous herb available in bulk-forming laxatives like Metamucil, absorbs fluid and makes patients feel as if they have eaten enough. Red peppers and mustard help patients lose weight more quickly by accelerating the metabolic rate. They also make people more thirsty, so they crave water instead of food. Walnuts contain serotonin, the brain chemical that tells the body it has eaten enough. Dandelion (Taraxacum officinale) can raise metabolism and counter a desire for sugary foods.

The amino acid 5-hydroxytryptophan, or 5-HTP, which is extracted from the seeds of the Griffonia simplicifolia plant, is thought to increase serotonin levels in the brain. Serotonin is a neurotransmitter, or brain chemical, that regulates mood and thus can be linked to mood-related eating behaviors. When physical and mental stress reduces serotonin levels in the body, 5-HTP may be helpful in regulating mood by boosting serotonin levels. Individuals should consult with their healthcare professional before taking 5-HTP, as the amino acid may interact with other medications and can have potentially serious side effects.

Acupressure and acupuncture can also suppress food cravings. Visualization and meditation can create and reinforce a positive self-image that enhances the patient's determination to lose weight. By improving physical strength, mental concentration, and emotional serenity, yoga can provide the same benefits. Also, patients who play soft, slow music during meals often find that they eat less food but enjoy it more.

Eating the correct ratio of protein, carbohydrates, and good-quality fats can help in weight loss via enhancement of metabolism. Support groups and self-help groups such as Overeaters Anonymous and TOPS (Taking Off Pounds Sensibly) that are informed about healthy, nutritious, and balanced diets can offer an individual the support he or she needs to maintain this type of eating regimen.

Allopathic Treatment

For individuals who are severely obese, dietary changes and behavior modification may be accompanied by surgery to reduce or bypass portions of the stomach or small intestine. The risks of obesity surgery have declined in recent years, but it is still only performed on patients for whom other strategies have failed and whose obesity seriously threatens their health. Other surgical procedures are not recommended, including liposuction, a purely cosmetic procedure in which a suction device is used to remove fat from beneath the skin, and jaw wiring, which can damage gums and teeth and cause painful muscle spasms.

A newer approach to weight loss is the development of functional foods, which are food products that incorporate natural compounds shown to help in weight loss programs. These compounds include carbohydrates with a low glycemic index, which help to suppress appetite; green tea extract, which increases the body's energy expenditure; and chromium, which encourages the body to burn stored fat rather than lean muscle tissue. Functional food products are currently undergoing clinical testing.

Appetite suppressant drugs are sometimes prescribed to aid in weight loss. These drugs work by increasing levels of serotonin or catecholamine, which are brain chemicals that control moods and feelings of fullness. Appetite suppressants, though, are not considered truly effective, since most of the weight lost while taking them is usually regained after stopping. Also, suppressants containing amphetamines can be potentially abused by patients. While most of the immediate side effects of these drugs are harmless, the long-term effects in many cases, are unknown. Two drugs, dexfenfluramine hydrochloride (Redux) and fenfluramine (Pondimin) as well as a combination fenfluramine-phentermine (Fen/Phen) drug, were taken off the market when they were shown to cause potentially fatal heart defects. In 1999, the United States Food and Drug Administration (FDA) approved a new prescription weight loss drug, Orlistat. Unlike other anti-obesity drugs that act as appetite suppressants, Orlistat encourages weight loss by inhibiting the body's ability to absorb dietary fat. The drug can cause side effects of abdominal cramping, gas, and diarrhea.

Other weight-loss medications available with a doctor's prescription include:

• Sibutramine (Meridia)
• Diethylpropion (Tenuate, Tenuate Dospan)
• Mazindol (Mazanor, Sanorex)
• Phendimetrazine (Bontril, Prelu-2)
• Phentermine (Adipex-P, Fastin, Ionamin, Oby-Cap)

Phenylpropanolamine (Acutrim, Dextarim) is the only nonprescription weight-loss drug approved by the FDA. These over-the-counter diet aids can boost weight loss by 5%. Combined with diet and exercise and used only with a doctor's approval, prescription anti-obesity medications enable some patients to lose 10% more weight than they otherwise would. Most patients regain lost weight after discontinuing use of either prescription medications or nonprescription weight-loss products.

Prescription medications or over-the-counter weight loss products can cause:

• constipation
• dry mouth
• headache
• irritability
• nausea
• nervousness
• sweating

None of the weight loss drugs should be used by patients taking monoamine oxidate inhibitors (MAO inhibitors).

Doctors sometimes prescribe fluoxetine (Prozac), an antidepressant that can increase weight loss by about 10%. Weight loss may be temporary and side effects of this medication include diarrhea, fatigue, insomnia, nausea, and thirst. Weight loss drugs currently being developed or tested include ones that can prevent fat absorption or digestion, reduce the desire for food and prompt the body to burn calories more quickly, and regulate the activity of substances that control eating habits and stimulate overeating.

Expected Results

As many as 85% of dieters who do not exercise on a regular basis regain their lost weight within two years. In five years, the figure rises to 90%. Repeatedly losing and regaining weight (yo-yo dieting) encourages the body to store fat and may increase a patient's risk of developing heart disease. The primary factor in achieving and maintaining weight loss is a lifelong commitment to regular exercise and sensible eating habits.

Prevention

Obesity experts suggest that a key to preventing excess weight gain is monitoring fat consumption rather than counting calories, and the National Cholesterol Education Program maintains that only 30% of calories should be derived from fat. Only one-third of those calories should be contained in saturated fats (the kind of fat found in high concentrations in meat, poultry, and dairy products). Because most people eat more than they think they do, keeping a detailed food diary is a useful way to assess eating habits. Eating three balanced, moderate-portion meals a day—with the main meal at mid-day—is a more effective way to prevent obesity than fasting or crash diets. Exercise increases the metabolic rate by creating muscle, which burns more calories than fat. When regular exercise is combined with regular, healthful meals, calories continue to burn at an accelerated rate for several hours. Finally, encouraging healthful habits in children is a key to preventing childhood obesity and the health problems that follow in adulthood.

New Directions in Obesity Treatment

The rapid rise in the incidence of obesity in the United States since 1990 has prompted researchers to look for new treatments. One approach involves the application of antidiabetes drugs to the treatment of obesity. Metformin (Glucophage), a drug that was approved by the Food and Dug Administration (FDA) in 1994 for the treatment of type 2 diabetes, shows promise in treating obesity associated with insulin resistance.

Another field of obesity research is the study of hormones, particularly leptin, which is produced by fat cells in the body, and ghrelin, which is secreted by cells in the lining of the stomach. Both hormones are known to affect appetite and the body's energy balance. Leptin is also related to reproductive function, while ghrelin stimulates the pituitary gland to release growth hormone. Further studies of these two hormones may lead to the development of new medications to control appetite and food intake.

A third approach to obesity treatment involves research into the social factors that encourage or reinforce weight gain in humans. Researchers are looking at such issues as the advertising and marketing of food products; media stereotypes of obesity; the development of eating disorders in adolescents and adults; and similar questions.

Resources

Books

Ackerman, Norman. 5-HTP: The Natural Way to Overcome Depression, Obesity, and Insomnia. New York: Bantam Books, 1999.

Flancbaum, Louis, MD, with Erica Manfred and Deborah Biskin. The Doctor's Guide to Weight Loss Surgery. West Hurley, NY: Fredonia Communications, 2001.

Harris, Dan R., ed. Diet and Nutrition Sourcebook. Detroit, MI: Omnigraphics, 1996.

"Nutritional Disorders: Obesity." Section 1, Chapter 5 in The Merck Manual of Diagnosis and Therapy, edited by Mark H. Beers, MD, and Robert Berkow, MD. Whitehouse Station, NJ: Merck Research Laboratories, 1999.

Periodicals

Aronne, L. J., and K. R. Segal. "Weight Gain in the Treatment of Mood Disorders." Journal of Clinical Psychiatry 64 (2003 Supplement 8): 22–29.

Bell, S. J., and G. K. Goodrick. "A Functional Food Product for the Management of Weight." Critical Reviews in Food Science and Nutrition 42 (March 2002): 163–178.

Brudnak, M. A. "Weight-Loss Drugs and Supplements: Are There Safer Alternatives?" Medical Hypotheses 58 (January 2002): 28–33.

Colquitt, J., A. Clegg, M. Sidhu, and P. Royle. "Surgery for Morbid Obesity." Cochrane Database Systems Review 2003: CD003641.

Espelund, U., T. K. Hansen, H. Orskov, and J. Frystyk. "Assessment of Ghrelin." APMIS Supplementum 109 (2003): 140–145.

Hundal, R. S., and S. E. Inzucchi. "Metformin: New Understandings, New Uses." Drugs 63 (2003): 1879–1894.

Pirozzo, S., C. Summerbell, C. Cameron, and P. Glasziou. "Advice on Low-Fat Diets for Obesity (Cochrane Review)." Cochrane Database Systems Review 2002: CD003640.

Schurgin, S., and R. D. Siegel. "Pharmacotherapy of Obesity: An Update." Nutrition in Clinical Care 6 (January-April 2003): 27–37.

Shekelle, P. G., M. L. Hardy, S. C. Morton, et al. "Efficacy and Safety of Ephedra and Ephedrine for Weight Loss and Athletic Performance: A Meta-Analysis." Journal of the American Medical Association 289 (March 26, 2003): 1537–1545.

Tataranni, P. A. "Treatment of Obesity: Should We Target the Individual or Society?" Current Pharmaceutical Design 9 (2003): 1151–1163.

Veniant, M. M., and C. P. LeBel. "Leptin: From Animals to Humans." Current Pharmaceutical Design 9 (2003): 811–818.

Organizations

American Dietetic Association. (800) 877-1600. .

American Obesity Association (AOA). 1250 24th Street NW, Suite 300, Washington, DC 20037. (202) 776-7711 or (800) 98-OBESE. .

American Society of Bariatric Physicians. 5453 East Evans Place, Denver, CO 80222-5234. (303) 770-2526. .

American Society for Bariatric Surgery. 7328 West University Avenue, Suite F, Gainesville, FL 32607. (352) 331-4900. .

North American Association for the Study of Obesity. 8630 Fenton St., Suite 412, Silver Spring, MD, 20910. (301) 563-6526. .

Overeaters Anonymous. P.O. Box 44020, Rio Rancho, New Mexico, 87174-4020. (505) 891-2664. .

Weight-control Information Network (WIN). 1 WIN Way, Bethesda, MD 20892-3665. (202) 828-1025 or (877) 946-4627.

[Article by: Paula Ford-Martin; Rebecca J. Frey, PhD]

Definition

Obesity is an abnormal accumulation of body fat, usually 20 percent or more over an individual's ideal body weight. Obesity is associated with increased risk of illness, disability, and death.

The branch of medicine that deals with the study and treatment of obesity is known as bariatrics. As obesity has become a major health problem in the United States, bariatrics has become a separate medical and surgical specialty.

Description

Childhood obesity is in the early 2000s a significant health problem in the United States. Obese children and adolescents are at increased risk for developing diabetes, hypertension, coronary artery disease, sleep apnea, orthopedic problems, and psychosocial disorders.

Obesity involves excessive weight gain and fat accumulation. For children and adolescents, obesity is defined in terms of body mass index (BMI) percentile. BMI is a formula that considers an individual's height and weight to determine body fat and health risk, and it is used differently for children and adolescents than it is for adults. In adults, BMI often misrepresents obesity because it does not consider healthy weight from muscle tissue; therefore, body fat percentage is considered a more accurate method for determining obesity in adults. In children and adolescents, because body fat changes as they mature, BMI is gender- and age-specific and plotted on gender-specific growth charts to determine BMI-forage. Curved lines on the chart (percentiles) are used by healthcare professionals to identify children and adolescents at risk for overweight and obesity. Children and adolescents with a BMI-for-age in the 85th to 95th percentile are considered overweight and at risk for obesity, and those with a BMI-for-age greater than the 95th percentile are considered obese.

Demographics

According to the American Obesity Association and the Centers for Disease Control and Prevention, 30.3 percent of children aged six to 11 years are overweight and 15.3 percent are obese, and 30.4 percent of adolescents aged 12 to 19 years are overweight and 15.5 percent are obese. From 1980 to 2004, the prevalence of obesity among children quadrupled, and the prevalence of obesity in adolescents more than doubled. Overweight and obesity is more prevalent in boys (32.7%) than girls (27.8%). Obesity is more common in African American, Hispanic American, and Native American children and adolescents, than among Caucasians of the same ages.

Causes and Symptoms

Although obesity can be a side effect of certain hormonal disorders or use of certain medications, the primary cause of obesity in children and adolescents is excess calorie consumption coupled with a sedentary lifestyle. Children and adolescents living in the twenty-first century are the most inactive generation ever. The majority of schools no longer offer daily physical education classes; and active leisure activities, such as bicycle riding, have been replaced by sedentary activities, such as television watching and playing computer games. Studies have documented dramatic changes in childhood food consumption from the 1970s to 2004. Fast foods and foods eaten at other restaurants have increased by 300 percent since 1977, and soft drink consumption has also increased significantly. In addition, standard meal portion sizes and snacking have increased.

Obesity is the result of a complex interaction of genetics and environmental factors. Genetics influence how the body regulates appetite and metabolism, while certain environmental factors encourage excess calorie consumption. The body requires a certain amount of energy for basic metabolism and to support additional physical activity. When calories consumed from food and beverages equal calories expended during physical activity, body weight is maintained. When calories consumed exceed calories expended, weight gain results. To gain one pound, 3,500 additional calories must be consumed. In American society, excess calories are easily consumed just by drinking soft drinks and eating "supersized" fast food meals. A sedentary lifestyle results in far fewer calories being burned daily.

The major symptoms of obesity are excessive weight gain and the presence of large amounts of fatty tissue. Obesity can cause a number of other conditions, including type 2 diabetes, hypertension, high cholesterol, joint pain, asthma, hypothyroidism, and gallstones. Type 2 diabetes, previously referred to as adult-onset diabetes, has increased dramatically in children, and this increase has been directly linked to obesity.

When to Call the Doctor

Overweight and obese children should be evaluated by a physician for diabetes, hypertension, high cholesterol, and other medical conditions that are influenced by excessive weight gain. Primary care physicians can be consulted for weight management counseling to help children lose weight.

Diagnosis

Obesity in children and adolescents is diagnosed using the BMI-for-age formula described above, which is used to define obesity. Comorbid conditions, such as diabetes and high cholesterol, are diagnosed using medical laboratory tests.

Treatment

As of 2004, no weight loss drugs were approved for use in children, although some drugs used to treat obesity are approved for use in adolescents age 16 years and older. A few drugs are under investigation for use in children. Although no drugs are specifically approved for pediatric weight loss, some physicians may prescribe them "off-label." Because the side effects of these medications in children are unknown, children should not use adult weight loss drugs.

For extremely obese adolescents, surgical procedures—called bariatric surgery—may be performed, but only rarely. These procedures involve significant surgical alteration of the digestive tract and require substantial modification of diet after the surgery to much less than 1,000 calories per day. The long-term effects on growth and development from severe postoperative calorie restriction are not unknown, and weight loss surgery should only be performed on adolescents as a last resort.

The most effective treatment for obese children and adolescents is behavior and lifestyle modification under the guidance of a physician or weight management specialist experienced in dealing with children and adolescents. Behavior and lifestyle modification involves the following:

• assessment of child's and family's eating habits
• implementation of a regular, safe exercise program and increasing active leisure activities
• limiting television viewing and other sedentary activities
• setting reasonable goals and monitoring goal achievement using positive, non-food-related incentives
• counseling regarding how to keep a food/activity diary to track progress
• extensive support by involving entire family and/or joining a weight loss group of peers

Alternative Treatment

Alternatives for weight loss involve the use of ephedra-containing drugs or herbal preparation or the use of diuretics and laxatives. Both of these practices are unsafe, especially for children and adolescents. Because ephedra can cause severe cardiac side effects, the Food and Drug Administration has issued warnings against its use. Diuretics and laxatives can result in severe dehydration and improper absorption of nutrients.

Acupressure and acupuncture can suppress food cravings. Visualization and meditation can create and reinforce a positive self-image that enhances the patient's determination to lose weight. By improving physical strength, mental concentration, and emotional serenity, yoga can provide the same benefits.

Given the drastic increase in childhood obesity, special summer programs and therapeutic schools have been formed to help children lose weight. Summer camp programs that focus on healthy eating and exercise habits are available for overweight and obese children. In addition, in early 2004, the first alternative school for overweight and obese children, which operates like other private and charter schools, but with a focus on healthy weight loss and maintenance, was established.

Prognosis

Obese and overweight children and adolescents are more likely to be obese or overweight as adults. According to the American Obesity Association, obese children aged 10 to 13 have a 70 percent chance of remaining obese for the rest of their lives. Obese individuals are at increased risk for many other diseases and early death. Behavior and lifestyle modification programs involving positive goal-setting, increased exercise, and group support can help children and adolescents successfully and safely lose weight.

Prevention

Obesity can be prevented by instilling healthy eating and regular exercise habits in children at an early age. Minimizing and structuring daily time for sedentary activities like television viewing and encouraging outdoor activities such as bicycle riding, walking, running, and active play, and active indoor activities such as dancing can help increase physical activity. Dietary modifications to help prevent obesity include limiting soft drink and fast food consumption, monitoring food portion sizes, and providing a well-balanced diet.

Nutritional Concerns

Nutrition is a primary factor for weight management of obese children and adolescents. Poor nutrition and dietary habits can lead to weight gain and obesity. Dietary modification is important for helping children lose weight and prevent obesity.

The following nutritional guidelines can help in the management of obesity:

• Limit soft drink consumption to one per day or less. One 12-ounce can of soda has 120 calories or more. Often, children and adolescents consume "super-size" sodas that may contain up to 1,000 calories.
• Limit fast food restaurant visits to one per week, and choose healthy options like grilled chicken and smaller sized portions of high-calorie items.
• Monitor food serving sizes.
• Increase consumption of fruits, vegetables, high-fiber foods, and whole-grain foods.
• Be aware that "low-fat" foods often substitute sugar for fat, and calories may actually be the same as the regular or high-fat version.

Parental Concerns

Parents of obese children and adolescents should be concerned for their current and future health, since obesity can result in diabetes, hypertension, and coronary artery disease. Losing weight can be very difficult for obese children, and parental support is essential for success. Because children model behavior after their parents, obesity often affects both parents and children. Parents should strive to have healthy eating habits and exercise regularly to be effective role models for their children. Making healthy eating and exercise a family priority is better for everyone and helps reinforce positive changes in behavior for the obese child.

Obese children and adolescents are more susceptible to eating disorders, negative self-esteem and body image, and depression due to peer influences. Counseling, peer group therapy, and family therapy may be required to support lifestyle modifications for obese children and adolescents.

Resources

Books

Burniat, Walter, et al. Child and Adolescent Obesity: Causes and Consequences, Prevention and Management. Cambridge, UK: Cambridge University Press, 2002.

Kiess, Wieland, et al. Obesity in Childhood and Adolescence. Basel, Switzerland: S. Karger AG, 2004.

Periodicals

Eissa, M. A. H., and K. B. Gunner. "Evaluation and Management of Obesity in Children and Adolescents." Journal of Pediatric Health Care 18(March 2004): 35–38.

Manson J. E., et al. "The Escalating Pandemics of Obesity and Sedentary Lifestyle." Archives of Internal Medicine 164(February 9, 2004): 249–258.

McWhorter, J. W., et al. "The Obese Child: Motivation as a Tool for Exercise." Journal of Pediatric Health Care 17(February 2003): 11–17.

Ritter, J. "Obese Teens Turn to Surgery of Last Resort." Chicago Sun-Times, March 29, 2004.

St-Onge M. P., et al. "Changes in Childhood Food Consumption Patterns: A Cause for Concern in Light of Increasing Body Weights." American Journal of Clinical Nutrition 78(December 2003): 1068–73.

Organizations

American Dietetic Association. Web site: www.eatright.org.

American Obesity Association (AOA). 1250 24th Street NW, Suite 300, Washington, DC 20037. Web site: www.obesity.org.

American Society of Bariatric Physicians. 5453 East Evans Place, Denver, CO 80222–5234. Web site: www.asbp.org.

American Society for Bariatric Surgery. 7328 West University Avenue, Suite F, Gainesville, FL 32607. Web site: www.asbs.org.

National Institute of Diabetes and Digestive and KidneyDiseases. 31 Center Drive, USC2560, Building 31, Room 9A-04, Bethesda, MD 20892–2560. Web site: www.niddk.nih/gov.

Shape Up America! Web site: www.shapeup.org/.

Web Sites

"BMI for Children and Teens." Centers for Disease Control and Prevention, 2004. Available online at www.cdc.gov/nccdphp/dnpa/bmi/bmi-for-age.htm (accessed October 26, 2004).

"Fitness for Your Child." IDEA Health and Fitness Association. Available online at www.ideafit.com/articles/fitness_child.asp (accessed October 26, 2004).

"Obesity in Youth." American Obesity Association. Available online at www.obesity.org/subs/fastfacts/obesity_youth.shtml (accessed October 26, 2004)

Other

Childhood Assessment Calculator. Available online at www.shapeup.org/oap/entry.php (accessed October 26, 2004).

[Article by: Jennifer E. Sisk, MA]

For more information on obesity, visit Britannica.com.

The storage of excessive amounts of fat, particularly under the skin and around certain internal organs. Obesity usually results from a positive energy balance and not having a balanced diet. Obesity is a well-recognized predisposing factor for a number of diseases, including diabetes mellitus, hypertension, and other cardiovascular diseases. Some medical experts estimate that life expectancy decreases by approximately 1% for each pound (about 450 g) of excess fat carried by an person of 45-50 years of age. Obesity is difficult to define quantitatively, but it is generally accepted that anyone who has a body mass index (BMI) greater than 30 is obese. According to this definition, it is possible to be obese without being over-weight. Conversely, muscular athletes may be over-weight without being obese.

Obesity is defined as having a body mass index (BMI), which is the relationship of mass to height, of 30 or more, or a weight of about 30 pounds over the maximum desirable for the individual's height. Those at least 100 pounds over their ideal weight are regarded as morbidly obese.

Obesity as a health problem was first discussed by Thomas Short (1690?–1772) in A Discourse Concerning the Causes and Effects of Corpulency. Together with A Method for Its Prevention and Cure (London, 1727). In 1829, the English physician William Wadd (1776–1829) published his Comments on Corpulency, Lineaments of Leanness, Mems on Diet and Dietetics. In 1863, Dr. William Banting (1779–1878) proposed his special "Banting diet" as a treatment for obesity. So-called Bantingism, a diet low in sugar and oily foods, swept across England, making it the first fad diet craze of national proportions. Largely compilations of unscientific speculations and opinions, these early works were supplanted by more systematic studies coming primarily from Germany and France throughout the latter half of the nineteenth century.

The United States did not come into the forefront of obesity research until Hugo Rony's Obesity and Leanness (1940). By the 1950s, the National Institutes of Health served as a catalyst for new investigations into the causes and nature of obesity, launching a new era in evaluating this potentially life-threatening condition. Researchers in the early twenty-first century understand obesity as a complex condition that can be approached from one of four different perspectives: behavioral/psychological aspects; physiological factors; cellular bases in the functions of fat cells; and genetic and molecular factors.

This last aspect came to scientists attention in the late twentieth century. In 1992, a specific gene responsible for obesity in mice was discovered and two others were identified shortly thereafter. Since this pathbreaking work, a number of genes thought to be responsible for predisposing humans to obesity have been uncovered. With the advent of new genetically targeted pharmaceuticals, the prospect of developing a "magic bullet" for people in this category might be on the horizon.

Still, the principal cause of obesity for most Americans is a combination of overeating and sedentary lifestyle. The Centers for Disease Control and Prevention (CDC) has kept data on obesity since 1985 through its Behavioral Risk Factor Surveillance System (BRFSS). The BRFSS reveals an alarming rise in overweight Americans. In 1985, no state had an obese population of 20 percent or more; in 1997, three states reported in that category; by 2000, a staggering 22 states had an obese population of 20 percent or greater. Of even more concern was the rising obesity rate among American children. The CDC reported skyrocketing obesity rates among children ages 12 to 17, from about 4 percent in 1963 to 11 percent by 1994.

As of 2000, 19.8 percent of the total U.S. population was obese. The prevalence of Americans (estimated as high as 47 million) with a metabolic syndrome (high blood pressure, high cholesterol, and high blood sugar and triglycerides) associated with obesity underscored a national need for stricter dietary regimens and more consistent exercise.

Bibliography

Bray, George A., Claude Bouchard, and W. P. T. James, eds. Handbook of Obesity. New York: Marcel Dekker, 1998.

Centers for Disease Control and Prevention. "Health Topic: Obesity/Overweight." Updated 30 May 2002. Available from http://www.cdc.gov/health/obesity.htm.

Pool, Robert. Fat: Fighting the Obesity Epidemic. New York: Oxford University Press, 2001.

Obesity and overweight now affect more than 50 percent of adult Americans. Diabetes mellitus, hypertension, heart disease, gallbladder disease, and some forms of cancer result from obesity. Whether these diseases are yet present or not, the obese individual should be encouraged to lose weight by appropriate methods to reduce the future likelihood that they will develop. Methods of weight loss include diet, nutritional education, self-help groups, and behavioral change. Under some circumstances drugs or surgery may be considered.

Definition and Measurement of Obesity

Obesity and overweight are best defined using the body mass index (BMI). This index is determined by dividing body weight in kilograms by the square of the height in meters: BMI = W/H². The normal rate for BMI is 18.5 to 25. A BMI between 25 and 30 kg/m² is defined as over-weight and a BMI above 30 kg/m² is defined as obesity (Table 1). Visceral fat can be used as an index of central adiposity. An increase in visceral fat reflects central obesity and increases health risks. The waist circumference is used to assess the amount of visceral obesity. A waist circumference in men of 40 inches (102 cm) or more, and in women, of 35 inches (88 cm) or more, is the threshold for defining central obesity (Table 1).

Prevalence of Overweight

More females than males are overweight at any age. The frequency of overweight increases with age to reach a peak at forty-five to fifty-four years in men and at age fifty-five to sixty-four in women. The National Health and Nutrition Examination Survey (NHANES) conducted by the U.S. government (published in 1993) found a BMI of 25 or more in 59.4 percent of men age twenty years or older and in 50.7 percent of women over the age of twenty years. The prevalence of obesity (BMI 30 or more) was 19.5 percent in men and 25.0 percent in women. The incidence of obesity continues to increase dramatically in the United States and elsewhere. A number of factors including age, sex, and physical inactivity influence the amount of body fat.

At birth, the human infant contains about 12 percent body fat. During the first years of life, body fat rises rapidly to reach a peak of about 25 percent by six months of age and then declines to 18 percent over the next ten years. At puberty, there is a significant increase in the percentage of body fat in females and a decrease in males. By age eighteen, males have approximately 15 to 18 percent body fat, and females have 25 to 28 percent. Between ages twenty and fifty, the fat content of males approximately doubles and that of females increases by about 50 percent. Total body weight, however, rises by only 10 to 15 percent: fat now accounts for a larger part of the body weight and lean body mass decreases.

Table 1

Risks Related to Obesity

As the BMI increases, there is a curvilinear rise in excess mortality. This excess mortality rises more rapidly when the BMI is above 30 kg/m². A BMI over 40 kg/m² is associated with a further increase in overall risk and for the risk of sudden death. The principal causes of the excess mortality associated with overweight include hypertension, stroke, and other cardiovascular diseases, diabetes mellitus, certain cancers, reproductive disorders, gall-bladder disease, and sudden death.

The insulin-resistant state or metabolic syndrome is strongly associated with visceral fat. It may include consequences such as glucose intolerance or type 2 diabetes mellitus, hypertension, polycystic ovarian syndrome, dyslipidemia (the state of abnormal—either higher or lower—values for blood fats), and other disorders. These are often responsive to weight loss, especially when this is achieved early and the loss is maintained.

Development of Obesity

Several mechanisms lead to obesity, including neuroendocrine imbalances, particular drugs, diet, reduced energy expenditure, and genetic factors that lead to certain syndromes and predisposition to obesity. Obesity can follow damage to the hypothalamus in the brain, but this is rare. Cushing's disease is somewhat more common and can result in obesity. Treatment should be directed at the cause of the increased formation of adrenal corticosteroids.

Treatment of diabetics with insulin, sulfonylureas, or thiazolidinediones (but not metformin) can increase hunger and food intake, resulting in weight gain. Treatment with some antidepressants, anti-epileptics, and neuroleptics can also increase body weight, as can cyproheptadine (a serotonin antagonist that produces weight gain), probably through effects on the monoamines (including norepinephrine, epinephrine, dopamine, histamine, and serotonin) in the central nervous system.

Eating a high-fat diet and excessive consumption of sugar-sweetened beverages and the prevalence of abundant varieties of food in cafeterias or supermarkets are dietary factors in the development of obesity. Reduced energy expenditure relative to energy intake is another major component. Energy expenditure can be divided into four parts.

An inactive individual at rest burns between 800 and 900 kilocalories during a twenty-four hour period. This rate is lower in females than in males, and declines with age, and could account for much of the increase in fat stores if food intake does not decline similarly. The effect of physical exercise on metabolism is variable but on average is responsible for about one-third of the daily energy expenditure. From a therapeutic point of view this component of energy expenditure is most easily manipulated. Dietary thermogenesis is the energy expenditure that follows the ingestion of a meal. Heat produced by eating may dissipate up to 10 percent of the ingested calories. These thermic effects of food are one type of metabolic "inefficiency" in the body, that is, where dietary calories are not available for "useful" work. In the obese, the thermic effects of food are reduced particularly in individuals with impaired glucose tolerance or diabetes. Acute over-or underfeeding will produce corresponding shifts in overall metabolism, which can be as large as 15 to 20 percent.

Genetic factors can produce some types of obesity that are easily recognized. Among these types of obesity are: (1) the Bardet-Biel syndrome, characterized by retinal degeneration, mental retardation, obesity, polydactyly, and hypogonadism; (2) the Alstrom syndrome, characterized by pigmentary retinopathy, nerve deafness, obesity, and diabetes mellitus; (3) Carpenter syndrome, characterized by acrocephaly (abnormalities in the facial and head bones), mental retardation, hypogonadism, obesity, and preaxial syndactyly (extra fingers or toes on one hand or foot); (4) the Cohen syndrome, characterized by mental retardation, obesity, hypotonia (reduced tone of the muscles, resulting in a "floppy" muscle mass), and characteristic facies (an appearance of the face that is typical of specific genetic diseases); (5) the Prader-Willi syndrome, characterized by hypotonia, mental retardation, hypogonadism, and obesity; and (6) the pro-opiomelanocortin (POMC) syndrome, characterized by defective production of POMC that is recognized as a red-headed fat child with a low plasma cortisol (a value that is below the normal range).

If both parents are obese, about 80 percent of their offspring will be obese. If only one parent is obese, the likelihood of obesity in the offspring falls to less than 10 percent. Studies with identical twins suggest that inheritance accounts for about 70 percent and environmental factors (diet, physical inactivity, or both) account for 30 percent of the variation in body weight. Deficiency of the gene leptin and deficiency of the leptin receptor are rare, but are associated with massive human obesity. Absence of convertase I has also been associated with obesity in one family. The most common defects associated with massive obesity are abnormalities in the melanocortin receptor system—up to 4 percent of massively obese people may have this type of defect.

Evaluation of the Obese Patient

A medical evaluation should include the expected medical history, family history, personal and social history, and review of the systems of the body with a particular focus on the medications that can cause weight gain. A physical examination should include an assessment of the patient's height, weight, waist circumference, blood pressure, and level of health risk due to obesity. Laboratory tests should include a lipid panel, glucose level, chemistry panel for hepatic (liver) function and uric acid, thyroid function testing, and, if indicated a cortisol level.

Evaluating Risk Using the Body Mass Index (BMI)

Individuals with a normal BMI (20–25 kg/m²) have little or no risk from obesity. Any individual in this weight range who wishes to lose weight for cosmetic reasons should do so only with conservative methods. Individuals with a BMI of greater than 25 to 29.9 kg/m² are in the low-risk group for developing heart disease, hypertension, gallbladder disease, and diabetes mellitus associated with obesity. They too should be encouraged to use low-risk treatments, such as caloric restriction and exercise. Individuals with a BMI of 27 to 30 kg/m² or more who have diseases related to obesity may use adjunctive pharmacotherapy for weight loss.

Individuals with a BMI of 30 to 40 kg/m², have moderate risk for developing diseases associated with obesity. Diet, drugs, and exercise would all appear to be appropriate forms of treatment. Individuals with significant degrees of excess weight often find exercise difficult. However, exercise is very important in helping to maintain weight loss. The use of weight loss medications, as an adjunct to treatment, may also be useful in this group. Individuals who have a BMI above 40 kg/m² have a high risk of developing diseases associated with their obesity. Moderate to severe restriction of calories is the first line of treatment, but for some of these patients surgery may be advisable.

Treatment of Obesity

Any diet must reduce an individual's caloric intake below daily caloric expenditure if it is to be successful. This requires an assessment of caloric requirements, by estimating caloric expenditure from desirable weight tables; for men, multiply desirable weight by 30 to 35 kilocalories/kilogram, (14–16 kilocalories/lb.); for women, multiply desirable weight by 25 to 30 kilocalories/kilogram (12–14 kilocalories/lb.). After assessing caloric requirements, a reasonable calorie deficit can be prescribed. A caloric deficit of 500 kilocalories/day (3,500 kilocalories/week) will produce the loss of approximately one lb. (0.45 kilograms) of fat tissue each week. Table 2 gives a list of diets divided into different levels of energy.

The very low calorie diet (below 800 kilocalories) was developed to facilitate the rate of weight loss since lower energy intake should lead to greater energy deficit. In free living people, however, diets with 400 kilocalories/day have not produced greater weight loss than those with 800 kilocalories/day, suggesting either that they are harder to adhere to or that there is an adaptation in energy expenditure. In either case, these diets should only be used under appropriate medical supervision.

Table 2

Types of diets. There are several types of diets with more than 800 kilocalories/day that usually have more than 1,200 kilocalories/day. They can be divided into several categories. These categories are based on the relative proportion of macronutrients included in the diet and whether they use special foods. For all diets it must be true that they reduce the calorie intake to produce a negative energy balance. Low-carbohydrate diets are touted because they produce ketosis (a state of increased ketones associated with diabetes and fasting) and allow you to eat all of the protein and fat you want. This ends up reducing total calorie intake to about 1,500 kilocalories/day. Since these diets generally have carbohydrate levels below 50 g./day they are ketogenic and can be monitored clinically by the appearance of ketones in the urine. They vary in the level of fiber that is employed. The Atkins diet has low fiber levels, the Sugar Busters diet higher fiber levels.

Low-fat diets recommend fat intake in the range of 10 to 20 percent of calories. The higher carbohydrate increases fiber intake. These diets were developed in a setting designed to reverse the atherosclerotic plaques associated with risks for heart disease, but because of the high fiber content they were often associated with weight loss. Moderate fat levels with higher carbohydrates are characteristic of many widely recommended "healthy diets." For weight loss, the New York Health Department recommends the Prudent Diet, which has stood the test of time.

The portion-controlled diet makes use of prepared foods that have a narrow range of calories. This includes liquid or powdered drinks as well as frozen or canned entrees that have about 300 kilocalories/meal. These can be combined conveniently and thus removes the problem of counting calories from the individual. A number of popular diets focus on a single food, and although nutritionally unbalanced, they are simple to follow and the monotony of single items tends to limit food intake.

Food Guide Pyramid. The Food Guide Pyramid provides an approach to evaluating the quality of your diet. At the bottom of the pyramid are the grains, beans, and starchy vegetables that provide vitamins, minerals, fiber, and energy; six or more servings are recommended. On the next level are the vegetables (3–5 servings) and the fruits (3–4 servings). On the third level are the meats, fish, poultry, and nuts (2–3 servings) along with the milk and yogurt (2–3 servings). At the top are the fats, sweets, and alcohol. Reducing the number of servings proportionally will provide you with a calorie-reduced diet. Most important for the dieter, however, is to sharply reduce the fats and sugar at the top of the pyramid and to reduce or eliminate alcoholic beverages. Not only do alcoholic beverages have calories, their consumption tends to reduce the individual's control in selecting the quality and quantity of foods to eat.

Changing behavioral patterns of eating. The basic principles of behavioral approaches for obesity can be summarized under the ABCs of eating.

• The A stands for antecedent. If one looks at eating as the response to events in the environment, then the antecedent events are those that trigger eating.
• The B stands for the behavior of eating. This includes among other things the place, the rate, and the frequency with which an individual eats. If the act of eating can be focused at one place with one plate and place setting it can help to provide control over eating.
• The C is the consequence of the eating. The feelings an individual has about eating can be altered, and rewards for changing eating patterns can be instituted.

Exercise and physical activity. The only part of energy expenditure that is amenable to significant manipulation is physical activity. During sleep, the lowest level of activity, approximately 0.8 kilocalories/minute is consumed. Thus, if an individual sleeps for an entire 24 hours, approximately 1,150 calories will be expended. Reclining increases this level to approximately 1.0-1.4 kilocalories/minute. Obese and diabetic patients should be encouraged to increase their physical activity for two reasons: First, it consumes calories, but second, and more important, exercise increases glucose utilization and may improve insulin sensitivity.

Drug treatment of obesity. Only a few drugs have been approved by the Food and Drug Administration for treatment of obesity. Studies following individuals who have used these drugs for two years have been published for sibutramine (Meridia) and orlistat (Xenical). Weight-loss drugs should be reserved for patients with moderate-or high-risk obesity (BMI >30 kg/m²) or a BMI above 27 if they have other significant diseases related to obesity. They should be considered for the patient who has failed to lose weight with other methods. Herbal products containing ephedra and an herbal source of caffeine can also produce weight loss when used in accordance with the package instructions.

Surgery. Gastric operations reduce the size of or bypass the stomach, but should be reserved for people with a BMI above 40 or when recommended by a physician.

The Obese Child

Estimates of the prevalence of obesity in children range from 3 to 15 percent. This figure has been rising more rapidly than in the rest of the population. The appearance of obesity in childhood and particularly adolescence is important because it most often persists into adult life. It may be a precursor to the appearance of type 2 diabetes in adolescents. The possibility of treatment should be considered for children who are above the seventy-fifth percentile of weight for height, and might be encouraged for those who are above the ninety-fifth percentile of weight for height. The treatment of prepubertal children should probably involve both parents and child since at this age the principal control of food availability is in the hands of the parents. For adolescents, however, it may be better to separate patient and parents, since the interaction between these groups may be part of the problem. Where growth has not reached its fullest extent, dietary restriction should attempt to reduce further weight gain. Severe caloric restriction and the use of appetite-suppressing drugs may slow height growth. For both children and adolescents, involvement in a regular exercise program is probably the first line of treatment.

Bibliography

Bessesen, D. H., and R. Kushner. Evaluation and Management of Obesity. Center for Obesity Research and Education. Philadelphia: Hanley and Belfus, 2002.

Bray, George A. Contemporary Diagnosis and Management of Obesity. Newtown, Pa.: Handbooks in Health Care, 1998.

National Heart, Lung, and Blood Institute (NHLBI). ClinicalGuidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. Bethesda, Md., 1998.

Yanovski, J., and S. Z. Yanovski. "Obesity." New England Journal of Medicine 346, no. 8 (21 February 2002): 591–602.

—George Bray

Quotes:

"Outside every fat man there was an even fatter man trying to close in." - Kingsley Amis

"I don't weigh a pound over one hundred and eighty and, what's more, I never did." - Fatty Arbuckle

"The obese is in a total delirium. For he is not only large, of a size opposed to normal morphology: he is larger than large. He no longer makes sense in some distinctive opposition, but in his excess, his redundancy." - Jean Baudrillard

"Every day the fat woman dies a series of small deaths." - Shelley Bovey

"I don't mind that I'm fat. You still get the same money." - Marlon Brando

"Imprisoned in every fat man, a thin one is wildly signaling to be let out." - Cyril Connolly

See more famous quotes about Obesity

The popular psychological interpretation of obesity is lack of self-esteem and overindulgence in fear and denial; layers of protection to insulate the dreamer from involvement or action; hopelessness and helplessness to express power and authority; fear that rejection will be the only reward for effort. Other possible meanings are the "fat cat" who ate the mouse, being full of oneself, or fattening up the livestock (for slaughter). (See also Fat).