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Metabolic adaptations in energy expenditure follow bariatric surgery

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August 9, 2016

Weight loss after Roux-en-Y gastric bypass, sleeve gastrectomy and laparoscopic adjustable gastric band in patients with obesity may lead to metabolic adaptations in energy expenditure, recently published data show.

Eric Ravussin, PhD, Boyd professor and associate executive director of clinical sciences at Pennington Biomedical Research Center in Baton Rouge, Louisiana, and colleagues evaluated 30 adults (27 women; mean age, 46 years; mean BMI, 47.2 kg/m2) who self-selected bariatric surgery (Roux-en-Y gastric bypass [RYGB], n = 5; sleeve gastrectomy, n = 9; laparoscopic adjustable gastric band [LAGB], n = 7) or a low-calorie diet (n = 9). The low-calorie diet consisted of 800 kcal/day for 8 weeks followed by weight maintenance.

Eric Ravussin

Eric Ravussin

Researchers sought to compare the changes in energy expenditure and circulating cardiometabolic markers 8 weeks and 1 year after bariatric surgery or the low-calorie diet intervention.

Degrees of weight loss were similar between the RYGB and sleeve gastrectomy groups (33%-36%) and were 16% in the LAGB and 4% in the low-calorie diet group after 1 year.

From baseline to week 8 and 1 year, 24-hour energy expenditure and sleeping energy expenditure were reduced in all study groups (P < .05 for all), but 24-hour energy expenditure between baseline and 8 weeks was not significantly reduced in the low-calorie group. From baseline to 8 weeks, after adjustment for free fat mass and fat mass, 24-hour energy expenditure was significantly reduced in all groups (RYGB, –145 kcal/day; sleeve gastrectomy, –254 kcal/day; LAGB, –178 kcal/day; low-calorie diet, –82 kcal/day), but at 1 year the changes persisted only in the RYGB (–124 kcal/day) and sleeve gastrectomy groups (–155 kcal/day). Trends were similar for sleeping energy expenditure in all surgery groups from baseline to 8 weeks (RYGB, –87 kcal/day; sleeve gastrectomy, –275 kcal/day; LAGB, –181 kcal/day), and the changes were maintained at 1 year (RYGB, –134 kcal/day; sleeve gastrectomy, –255 kcal/day; LAGB, –220 kcal/day). Compared with the low-calorie diet group, sleep energy expenditure reductions were higher in all surgery groups at 1 year (P < .05 for all).

One year after RYGB or sleeve gastrectomy, plasma HDL and total and high molecular weight adiponectin were increased, whereas triglycerides and high-sensitivity C-reactive protein levels were reduced.

“We found that metabolic adaptation of [approximately] 150 kcal [per day] occurs up to 1 year after RYGB, [sleeve gastrectomy] and LABG surgery,” the researchers wrote. “Our findings in obese individuals after bariatric surgery extend those already available after diet-induced weight loss, suggesting that a deficit in energy adaptation may be a homeostatic mechanism encouraging weight regain. Future studies are required to examine whether these effects remain beyond 1 year and contribute to the metabolic benefits of bariatric surgery.” – by Amber Cox

Disclosure: The researchers report no relevant financial disclosures.

itj+ Perspective

Philip Schauer

Philip Schauer

The authors of the study showed that some degree of metabolic adaption occurs after bariatric surgery, especially gastric bypass and sleeve gastrectomy.
Metabolic adaption, which is a greater reduction in energy expenditure than expected after weight loss, is one explanation why it’s so difficult to maintain weight loss regardless of the manner of weight loss (diet or surgery). Many believe that this metabolic adaption is a physiologic adaption to maintain body weight.
This is one of the first studies that evaluates in this manner metabolic adaption after bariatric surgery. What’s interesting is that despite metabolic adaption, patients who had surgery maintained significant weight loss — 33% to 36% body weight loss. These findings suggest that metabolic adaption after surgery might indeed be less than what is seen after severe weight loss after diet.
A recent study by Fothergill and colleagues (Fothergill E, et al. Obesity. 2016;doi:10.1002/oby.21538.) showed that metabolic adaption of minus 500 calories/day occurs after extreme weight loss from dietary therapy. Thus, one possible explanation or hypothesis as to why patients maintain greater weight loss after surgery compared to diet therapy is the degree of metabolic adaption, which appears to be less after surgery. Clearly, studies that directly compare equivalent amount of weight loss after surgery and diet therapy are needed to substantiate this hypothesis.

Philip Schauer, MD
Bariatric Surgeon, Director of Cleveland Clinic’s Bariatric & Metabolic Institute

Disclosure: Schauer reports being a paid consultant for Ethicon and primary investigator of The STAMPEDE clinical trial.