[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.