ABSTRACT
In most people, body fat and weight remain remarkably constant over long periods, despite fluctuations in food intake and activity level. It appears that when energy intake or activity level changes, the body compensates to prevent a significant change in body weight and fat. This is mainly because the body has the ability to balance energy intake and expenditure at a particular level or set point. For example, the body takes in an average of 2500 kcal per day, or nearly one million kilocalories per year. However, the average gain of 0.7 kg (1.5 lb) of fat each year represents an imbalance of only 5250 kcal between energy intake and expenditure (3500 kcal is equivalent of 0.45 kg (1 lb) of adipose tissue). This translates into a surplus of less than 15 kcal per day.
