Expert Q&A

Metabolic Benefits of Weight Loss on Diabetes

It is known that gastric bypass surgery is an effective method for treating and potentially reversing type 2 diabetes mellitus in patients with severe obesity, even leading to many no longer requiring diabetes medication. In a new study, researchers set out to determine whether the weight loss or the surgery itself were behind these results.1

The study measured 2 groups of patients with severe obesity—one group that underwent gastric bypass surgery and another that lost a similar percentage of body fat through diet alone. The researchers found similar metabolic responses in both groups that contributed to the reduced need for diabetes medication.

Consultant360 reached out to lead researcher Samuel Klein, MD, who is the director of the Center for Human Nutrition at Washington University in St. Louis, about the research and its implications.


Consultant360: You found that similar metabolic improvements occurred whether patients lost weight as a result of gastric bypass surgery or through diet alone. Was this result surprising?

Samuel Klein: We were disappointed but not surprised. We know that weight loss alone has profound beneficial effects on metabolic health. The problem is that it is very difficult for most people with obesity to lose weight and maintain long-term weight loss.

C360: What are the key takeaways from your study? How do you suggest health care providers implement these key takeaways into their everyday practice?

SK: Roux-en-Y gastric bypass (RYGB) surgery simultaneously improves multiple metabolic factors that regulate blood glucose control and metabolic health, including multi-organ insulin sensitivity, β-cell function (the ability of the pancreas to make and secrete appropriate amounts of insulin), and 24-hour blood glucose and insulin profiles. Even though weight loss itself is the primary mechanism responsible for the beneficial effects of RYGB surgery, this does not diminish the importance of RYGB as a therapy for patients with obesity and type 2 diabetes mellitus. RYGB improves overall health and reduces, or even completely eliminates, the need for diabetes medications 

C360: What knowledge gaps still exist concerning how gastric bypass surgery affects weight loss?

SK: The most important, but poorly understood, aspect of RYGB surgery is its remarkable effect on body weight. We do not understand why RYGB reduces the drive to eat and is so successful in producing long-term weight loss. A better understanding of the mechanisms responsible for the effect of RYGB on food intake could lead to new and effective nonsurgical therapeutic options.



Yoshino M, Kayser BD, Yoshino J, et al. Effects of diet versus gastric bypass on metabolic function in diabetes. August 20, 2020. N Engl J Med2020;383:721-32 DOI:10.1056/NEJMoa2003697