Dietary-Induced Energy Expenditure: A Human Study

Abstract

<p>Indirect calorimetry was used to examine energy expenditure at rest and dietary-induced energy expenditure in normal-weight and overweight volunteers, whose daily energy intakes were similar. The influences of exercise, exercise training, and insulin on dietary-induced energy expenditure were also assessed. At rest energy expenditure was 70.3 kcals/hour in the overweight volunteers, 7.4 kcals/ hour greater than in the normal-weight volunteers. Consumption of a mixed meal of nearly 1000 kcals elicited similar increases in energy expenditure in the normal-weight and overweight volunteers of 10.8 kcals/hour and 12.5 kcals/hour respectively. The results refute the suggestion that a deficiency in energy expenditure at rest or in dietary-induced energy expenditure could be responsible for the greater propensity towards obesity in the overweight volunteers.</p> <p>When exercise preceded the meal, the oxygen debt of exercise summated with the dietary-induced energy expenditure in the normal-weight group. The post-prandial response in the overweight group was similar whether or not exercise preceded the meal, even though the metabolic response to exercise alone was not impaired in the overweight group.</p> <p>Six volunteers (four normal-weight and two over-weight) completed an exercise training programme, and increased their fitness level. However, dietary-induced energy expenditure in response to the 1000 kcal meal was similar before and after training.</p> <p>Hyperinsulinaemia in six normal-weight, non-diabetic volunteers did not influence the post-prandial energy response, although the infusion of insulin and glucose itself elicited an obligatory increase in energy expenditure.</p> <p>The work described in the thesis thus suggests that in mildly overweight individuals there is no evidence that reductions in post-prandial energy expenditure account for their excess weight, but that the lack of a further increase in post-prandial energy expenditure following exercise may do so. The results of the thesis indicate that exercise training does not alter post-prandial energy expenditure, and that hyperinsulinaemia does not influence post-prandial energy expenditure.</p>