Dietary Fat, Carbohydrate Balance and Weight Maintenance: Effects of Exercise.
Most individuals maintain a stable bodyweight during long periods of their life, indicating that energy intake and energy expenditure, although quite variable from day to day, tend to remain adjusted to each other in the average. Obviously, such a steady state is likely to be sustained only if the fuel mix oxidized by the body is equivalent, in its average composition, to the nutrient content of the diet consumed, so that protein balance, carbohydrate balance, and fat balance are all achieved.
Because deviations from these balances undoubtedly occur from day to day, the maintenance of a long-term steady state of weight maintenance further implies that depletion or accumulation of body constituents elicits three possible corrective responses: to alter the composition of the substrate mix used for energy generation, to influence food intake, and/or to alter the rate of energy expenditure.
This discussion considers the consequences that the constraint of having to adjust the composition of the fuel mix oxidized to the nutrient distribution in the diet may have in the regulation of body weight. This aspect of the problem is not usually dealt with when the regulation of the overall energy balance is studied because, often, only the sums of the energy contents of the nutrients and of the substrates oxidized are taken into consideration.