ABSTRACT
There is no doubt that weight gain occurs when energy intake exceeds energy expenditure, that weight loss occurs when energy expenditure exceeds intake, and that weight maintenance results from a balance between energy intake and expenditure. Calorie intake is by definition a determinant of energy balance and, by definition, when a person is in energy balance, weight is maintained. It is not the purpose of this chapter to question whether calorie intake is part of the energy balance equation and therefore a determinant of energy balance. There is no scientific basis or empirical evidence to suggest otherwise. Rather, the purpose of this chapter is to determine what dietary composition, dietary behaviors, and other lifestyle factors promote energy balance by facilitating the individual’s ability to balance calorie intake with energy expenditure. Given that the question as to whether calories matter is answered by the law of thermodynamics, the more interesting question, and the one addressed in this section, is: what is the relative contribution of energy intake to the recent rise in obesity rate?
