[Energy expenditure and body composition in severe and morbid obese women after gastric bypass].

BACKGROUND The effects of gastric bypass (GBP) on resting energy expenditure (REE) are not well known. AIM To evaluate the changes in REE and its relationship with body composition in severe and morbid obese women before and six and twelve months after GBP. PATIENTS AND METHODS Twenty three women aged 37+/-10 years, with a body mass index of 44+/-4 kg/m(2), were evaluated before, six and twelve months after GBP. REE was measured in a Deltatrac indirect calorimeter and expressed as kcal/day Fat mass (EM), and fat free mass (EEM) were determined by double beam X-ray densitometry (DEXA). RESULTS Body weight reduction six and twelve months after GBP was 29.0+/-4.3 and 35.8+/-6.9%, respectively. The best predictor of weight reduction was initial weight (p <0.01). At six and twelve months, REE decreased by 291.7+/-260.0 and 353.8+/-378.4 kcal/day, respectively. In the same periods REE/kg body weight increased by 3.3 and 4.8 kcal/kg respectively, compared to baseline. REE/kg EEM was unchanged. CONCLUSIONS GBP was associated with significant changes in body composition after six and twelve months. However, despite weight reduction, resting energy expenditure per fat free mass unit did not change significantly.