Adaptation of energy metabolism of overweight women to low-energy intake, studied with whole-body calorimeters.

In 14 overweight women, 24-h energy expenditure (EE) was measured in a whole-body indirect calorimeter: before weight reduction (100% diet), after 1 wk on a 4.2-MJ diet, after 8 wk on 4.2-MJ diet, after weight reduction on 100% diet. Data of two subjects were excluded. Mean body weight declined from 93.3 +/- 7.4 (mean +/- SD) to 83.4 +/- 7.7 kg; 24-hEE decreased from 10.52 +/- 0.83 MJ on the 100% diet to 9.58 +/- 0.75 MJ on the 4.2-MJ diet. After 8 wk, 24-hEE had decreased by 15% of the initial 24-hEE to 8.92 +/- 0.65 MJ. After refeeding (1 wk), it increased to 9.45 +/- 0.75 MJ. Calculated energy requirement before weight reduction was 10.62 +/- 0.88 MJ/day; after weight reduction, 9.39 +/- 0.79 MJ/day. The decrease was more than that predicted from the change in body weight and body composition. An adaptation probably occurs, which may be metabolic.