Postprandial thermogenesis in post-obese women and weight-matched controls.

Postprandial thermogenesis was assessed on two occasions in six weight-stable post-obese women, with a mean weight loss of 21.9 (range 10.1-43.3) kg, and six control subjects who had never been overweight. The two groups of subjects were closely matched for weight, height, body mass index and age. The energy load of the test meal was proportional to each subject's energy requirement. Energy expenditure was monitored for 40 min before and 245 min after the meal by ventilated hood indirect calorimetry. Mean baseline energy expenditure was 3.65 (s.e.m. 0.22) kJ/min in the post-obese, and 3.73 (s.e.m. 0.17) kJ/min in the control subjects (P greater than 0.5). Mean postprandial energy expenditure was 4.50 (s.e.m. 0.25) kJ/min in the post-obese women and 4.61 (s.e.m. 0.18) kJ/min in the control women (P greater than 0.5). The mean thermic response, expressed as percentage of baseline energy expenditure, was 23.5 per cent (s.e.m. 1.4 per cent) in the post-obese and 24.1 per cent (s.e.m. 1.6 per cent) in the control subjects (P greater than 0.5). When expressed as percentage of the meal energy, the response was 7.9 per cent (s.e.m. 0.4 per cent) in the post-obese, and 7.4 per cent (s.e.m. 0.4 per cent) in the control subjects (P greater than 0.1). Reproducibility of duplicate measurements of postprandial thermogenesis, estimated as within-subject coefficient of variation, was 16.6 per cent when expressed as percentage increase over baseline energy expenditure, and 16.4 per cent when expressed as percentage of meal energy ingested. The present results do not support an impaired postprandial thermogenesis in women with a tendency to obesity, and suggest that part of the controversy in this field may be due to differences in study design and to the poor reproducibility of this measurement.