Changes in Resting Energy Expenditure and Body Composition after Weight Loss following Roux-en-Y Gastric Bypass

Abstract

Background: The objective of this study was to evaluate changes in resting energy expenditure (REE), body composition and metabolic parameters, and to investigate predictors of the results in seriously obese patients after Roux-en-Y gastric bypass (RYGBP).Methods: 31 patients (BMI 44.4 ± 4.8 kg/m 2 ; 27 female, 4 male; 37.3 ± 11.1 y) were evaluated at baseline and 6 months after RYGBP. Weight, REE, waist circumference (WC), fat mass (FM) and fat-free mass (FFM), physical activity, food intake, fasting glucose (GLU), insulin (INS), HOMA-IR and lipid concentrations were measured. Results: At 6 months, percentage of weight loss (%WL) was 29.0 ± 4.4% and percentage of excess weight loss was (%EWL) 59.7 ± 12.3%. FM loss corresponded to 77.1 ± 12.2% of the weight loss. REE decreased from 33.4 ± 4.1 to 30.1±2.6 kcal/kg FFM (P<0.05). Significant decreases (P<0.001) were observed in GLU, INS, HOMA-IR, LDL-cholesterol and triglycerides. %EWL was correlated with baseline INS (r=0.44; P=0.014), baseline HOMA (r=0.43; P=0.017), change in %FM (r=0.67; P<0.001) and change in WC (r=0.5; P<0.01). Decrease in REE/FFM (%) was positively correlated with baseline REE/FFM% (r=0.51; P<0.005) and change in %FM (r=0.69; P<0.001). Initial REE/FFM, baseline energy balance and FM change explain 90% of REE/FFM decrease.Conclusion: RYGBP was an effective procedure to induce significant weight loss, fat mass loss and improvement in metabolic parameters in the short term. Metabolic adaptation was not related to FFM wasting but to a higher baseline REE. Fasting hyperinsulinemia was the best single predictor of weight loss after RYGBP.

The physiology underlying Roux-en-Y gastric bypass: a status report

“…The human literature is not entirely consistent in respect to RYGB-induced changes in overall energy expenditure (23,31,32,42,152,153). A recent review indicated that total energy expenditure in humans often decreases due to the decrease in fat-free and fat mass but that diet-induced thermogenesis is often increased (please see also below) (145).…”

“…The majority of data collected with the help of preclinical studies seems to be consistent with findings in humans. However, changes in energy expenditure after RYGB seem to be less consistent in humans compared with most animal models, but this may be related to the much larger heterogeneity of study populations in humans compared with laboratory animals (23,31,145,146,152).…”

“…The majority of data collected with the help of preclinical studies seems to be consistent with findings in humans. However, changes in energy expenditure after RYGB seem to be less consistent in humans compared with most animal models, but this may be related to the much larger heterogeneity of study populations in humans compared with laboratory animals (23,31,145,146,152).Research with animal models helped to elucidate some of the physiological mechanisms that potentially underlie the treatment success of bariatric surgery. Further, animal experiments allow the assessment of unbiased data that are e.g., independent of nutritional counseling in RYGB patients or other medical advice.…”

Gasto energético y composición corporal en mujeres con obesidad severa y mórbida sometidas a bypass gástrico

“…En este estudio, las pacientes bajaron 28,4% del peso inicial al sexto mes y 35% del peso inicial al año de la operación, cifras similares a las observadas en otros estudios 8,18,24 . La reducción de MLG correspondió a 30% del peso reducido al año postoperatorio; esta disminución es similar a la observada con tratamientos médicos 25,26 y quirúr-gicos 18,24 contra la obesidad, aunque mayor que la reportada por otros estudios 14 .…”

Gastrointestinal hormones, energy balance and bariatric surgery

“…The magnitude of decreased resting energy expenditure was proportional to the postoperative weight loss. In another study, Carrasco et al 47 evaluated changes in resting energy expenditure in 31 morbidly obese patients, 6 months before and after GBP, and also found a significant reduction in resting energy expenditure. Unfortunately, the authors did not include a control group in their analysis.…”