The dynamics of weight loss after gastric partition for gross obesity.

Energy intake and expenditure have been assessed in patients before gastric partition for gross obesity, 3 months after operation when they were still losing weight and at 12 months when weight loss was complete and stable. Food intake was drastically reduced after surgery and the energy deficit so produced was sufficient to account completely for the weight loss, even when allowance was made for an adaptive reduction in energy expenditure. In a majority of patients, the eventual reduction in expenditure parallels the regression of metabolic rate against body mass index for a population of stable obese patients. However, the reduction in resting metabolic rate was maximal soon after the operation, when weight loss was far from complete. Weight loss stabilized at about 6 months, not due to a further reduction in energy expenditure but because energy intake recovered until the patient was again in energy balance.