The most common is lactose intolerance.
Glucose is the most common carbohydrate monomer in living organisms. It serves as a primary source of energy and is used in various metabolic pathways for cell function.
Carbohydrate, in fact it is the most common.
Glucose
The most common hazard associated with NSAID use is gastrointestinal intolerance and ulceration
Adult lactose intolerance is the most common of all enzyme deficiencies, and it is estimated that 30-50 million Americans have this condition.
Diabetes mellitus is the most common disorder of carbohydrate metabolism, and it is abbreviated DM.
Glucose is the most important carbohydrate to all living things because it is the primary source of energy for cells. It is broken down through cellular respiration to produce ATP, which is used for various cellular processes.
Orthostatic intolerance more frequently affects women; female-to-male ratio is at least 4:1. It is most common in people less than 35 years of age.
Celiac disease and gluten sensitivity both are linked to peripheral neuropathy, or nerve problems. Neuropathy is the second most common symptom of gluten intolerance and for a percentage of those with celiac/gluten intolerance neuropathy is sometimes the first or only symptom.
Sugar is actually a crystalline carbohydrate. There are multiple types of sugars, the most common being sucrose, lactose and fructose. So, to answer your question, sugar is a carbohydrate, not a fat.
The most common carbohydrate energy source for most organisms is glucose. Other common sugars are fructose and galactose, but glucose by far is the most common. Glucose is not only the most common as a simple sugar (monosaccharide), but also as the basic link in larger polysaccharides, including the disaccharide sucrose and the polymers glycogen and amylose.
There are three classifications of lactose intolerance. The two most common are environmentally induced, the third is a result of genetics.1. Primary lactose intolerance. Environmentally induced when weaning a child in non-dairy consuming societies. This is found in many Asian and African cultures, where industrialized and commercial dairy products are uncommon.2. Secondary lactose intolerance. Environmentally induced, resulting from certain gastrointestinal diseases, including exposure tointestinal parasites such as Giardia lamblia. In such cases the production of lactase may be permanently disrupted. A very common cause of temporary lactose intolerance is gastroenteritis, particularly when the gastroenteritis is caused by rotavirus. Another form of temporary lactose intolerance is lactose overload in infants.3. Congenital lactase deficiency. A genetic disorder which prevents enzymatic production of lactase. Present at birth, and diagnosed in early infancy.