Absence of increased thermogenesis during short-term overfeeding in normal and overweight women

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Abstract
Dietary thermogenesis was studied under carefully controlled dietary and physical activity plans. Eight females, four normal and four overweight, were kept in a metabolic ward and O2 consumption was measured during three periods. The first (5 days) served as a baseline control, in which the subjects ate ad libitum and retained their usual weight. In the second period (5 days), each subject ate a daily excess averaging about 2,300 kcal superimposed on her normal daily intake in the first period. The subjects were then released and dieted at home. After each subject had lost between 2 and 5 kg., she was called for a third period of 2 days during which she ate the same daily excess as in two matching days in the second period. O2 consumption was measured three times daily: at rest after arising in the morning, and during two daily exercise periods, one before breakfast, and the other after breakfast. Leisure time activity was controlled throughout the experiment. It was found that: 1) There was no increase in O2 consumption during the two overfeeding periods as compared to control, either at rest or during the exercise periods. 2) There was no difference between the normal and overweight subjects in their responses to overfeeding. 3) There was no increased efficiency in energy utilization during overfeeding which followed a state of energy deficit, as compared to overfeeding which followed a state of energy balance. It is suggested that an increased dietary thermogenesis is not a factor in the regulation of energy balance during periods of overeating lasting several days only.