Long-Term Study Reveals Sustained Metabolic Adaptation After Gastric Bypass Surgery

Gastric bypass surgery (GBP) leads to significant long-term weight loss and improvements in health, according to results published in the International Journal of Obesity.

A recent study aimed to evaluate metabolic adaptation in patients who underwent GBP by assessing their basal metabolic rate (BMR) over 24 months. The study included 31 patients and 30 weight-stable comparators, with BMR and body composition measured before surgery and at 3, 12, and 24 months postsurgery.

“It was hypothesised that the expected down regulation of BMR observed after weight loss, over and above that explained by changes in fat mass (FM) and fat-free mass (FFM), would be attenuated in patients by 3-month post -surgery,” wrote Fathimath Naseer, Nutrition Innovation Centre for Food and Health (NICHE), Ulster University, Coleraine, United Kingdom, and coauthors.

Results showed that patients experienced a significant reduction in weight, losing 25.6% of their total body weight over 2 years, primarily due to a 40% reduction in FM and an 11% reduction in FFM. By 3 months postsurgery, the patients' FFM was similar to that of the comparator group, but their FM remained higher, resulting in a decreased body fat percentage from 50% to 40% over 24 months.

The study also found that BMR decreased by 22% after surgery, aligning with the comparator group postsurgery. Metabolic adaptation, defined as the difference between observed and predicted BMR, was significant at 3, 12, and 24 months postsurgery, indicating the body's resistance to weight loss. Positive correlations were observed between changes in FFM and BMR at 12 and 24 months, suggesting that maintaining FFM may help sustain BMR.

“Understanding the underlying mechanisms and predictors that attenuate metabolic adaptation following GBP could potentially help the development of treatments to aid weight loss maintenance after non-surgical weight loss or even weight regain after surgery,” concluded the study authors.

Reference

Naseer F, Zhang SD, Miras AD, et al. Metabolic adaptation following gastric bypass surgery: results from a 2-year observational study. Int J Obes (Lond). Published online September 3, 2024. doi:10.1038/s41366-024-01585-5