About 10% of the total calories intake.
There are so many types of foods out there, that it really depends on what the food is.
twenty
3,680 per year
Use the equation E=mc2 . where c is the speed of light and multiply that by how many million milligrams you've got. Different foods have different calories not because they have different milligrams or weights, but because they are different foods altogether. A milligram of chocolate would have more calories than a milligram of water because you get more energy from eating a milligram of chocolate than drinking a milligram of water.
The United States Department of Agriculture has a "National Nutrient Database" which contains details of calories and nutrients in many different foods. http://www.nal.usda.gov/fnic/foodcomp/search/
There is no such thing as "common foods". Foods are specific sometimes ot certain regions or areas, and there are so many foods out there. Please be more specific in your question, so WikiAnswers can provide you with the best possible answer.
It's basically how many calories your body burns through digesting, absorbing, and using food.
5000 calories
Dieting sites can explain the number of calories in different foods. If you are looking for information on what calories actually are, a scientific website such as Roth Consulting will have this information. Wikipedia is another good resource to learn about calories.
For any food to have "negative" calories, eating and digesting it would have to consume more calories than the food provides, resulting in a net "negative" number. While this is claimed for low calorie foods such as cabbage, celery, lemon, lime, grapefruit- that is not true- they all have positive calories- but very few of them.
Not enough to cancel out the calories of the orange. There are no "negative calorie" foods, with the exception of celery.
It all depends on what foods are in the meal and the serving size.