Surgical Weight Loss: Impact on Energy Expenditure

Abstract

Diet-induced weight loss is often limited in its magnitude and often of short duration, followed by weight regain. On the contrary, bariatric surgery now commonly used in the treatment of severe obesity favors large and sustained weight loss, with resolution or improvement of most obesity-associated comorbidities. The mechanisms of sustained weight loss are not well understood. Whether changes in the various components of energy expenditure favor weight maintenance after bariatric surgery is unclear. While the impact of diet-induced weight loss on energy expenditure has been widely studied and reviewed, the impact of bariatric surgery on total energy expenditure, resting energy expenditure, and diet-induced thermogenesis remains unclear. Here, we review data on energy expenditure after bariatric surgery from animal and human studies. Bariatric surgery results in decreased total energy expenditure, mainly due to reduced resting energy expenditure and explained by a decreased in both fat-free mass and fat mass. Limited data suggest increased diet-induced thermogenesis after gastric bypass, a surgery that results in gut anatomical changes and modified the digestion processes. Physical activity and sustained intakes of dietary protein may be the best strategies available to increase non-resting and then total energy expenditure, as well as to prevent the decline in lean mass and resting energy expenditure.

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

“…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). Nonetheless, some studies in humans report an increase in total energy expenditure, similar to the data in rodents.…”

“…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.…”

Laparoscopic sleeve gastrectomy and Roux-en-Y gastric bypass lead to equal changes in body composition and energy metabolism 17 months postoperatively: a prospective randomized trial

“…However, fat tissue as a metabolically active body component contributes to REE as well, as demonstrated by Das et al (21) . Various studies have been carried out so far to compare the effect of different bariatric procedures on resting energy expenditure and body composition (30) . To our knowledge, no randomized study compared sleeve gastrectomy to the gastric bypass procedure in terms of REE by means of indirect calorimetry.…”

Patients’ strategies for eating after gastric bypass surgery: a qualitative study

“…1,2 Nevertheless, the evaluation of results after bariatric surgery continues to be debated, as the variation in weight loss is hard to explain. 3 Moreover, weight regain after surgery is a recurrent element in long-term (410-year) follow-up studies. 4 Failure rates of up to 35% have been reported with respect to expected weight loss over time.…”