We all need energy to function and we get this energy from the foods we eat. The most efficient way for cells to harvest energy stored in food is through cellular respiration, a catabolic pathway for the production of adenosine triphosphate (ATP). ATP, a high energy molecule, is expended by working cells.
An Apple a Day. The calories in a McIntosh apple depend on its size. According to the U.S. Department of Agriculture, a medium-sized apple with its skin has about 95 calories. Eating an unpeeled apple is moderately higher in calories than a peeled apple, but don't rush to peel your apple.
Apples have about 80 calories each. But no, they're VERY good for you. Apples make you feel full because of the fiber, which your body needs for a healthy digestive system. Also it helps lower your cholesterol and prevent heart disease (an apple a day keeps the doctor away!!) I eat an apple every day.