Effects of Diet versus Gastric Bypass on Metabolic Function in Diabetes
Evidence from past suggests surgical procedure involving a bypass of the upper gastrointestinal tract, such as Roux-en-Y gastric bypass, to have unique therapeutic effects on glycemic control. Yoshino and colleagues (2020) investigated the study entitled “Effects of Diet versus Gastric Bypass on Metabolic Function in Diabetes” published in the “New England Journal of Medicine”. The summary of the study is given below:
Objectives:
To determine the therapeutic metabolic effect of gastric bypass independent of weight loss in people with obesity and type 2 diabetes.
Method:
22 patients with obesity and diabetes participated in the study. Metabolic regulators of glucose homeostasis were evaluated before and after matched (approximately 18%) weight loss induced by gastric bypass (surgery group) or diet alone (diet group). The primary findings included the change in hepatic insulin sensitivity, which was assessed by the infusion of insulin at low rates. Secondary outcomes include changes in muscle insulin sensitivity, beta-cell function, and 24-hour plasma glucose and insulin profiles.
Findings:
The study reports considerable improvements in body composition (body fat mass, intraabdominal adipose tissue volume, and intrahepatic triglyceride content), 24-hour plasma glucose, free fatty acid, and insulin profiles; beta-cell function, insulin sensitivity in the liver, skeletal muscle, and adipose tissue in both the groups (gastric bypass or diet therapy) after marked weight loss. Additionally, a similar improvement in the ability of insulin to suppress both glucose production and lipolysis and to stimulate glucose disposal was observed in both groups. Weight loss is also reported to increase beta-cell function because of an increase in both beta-cell glucose sensitivity and whole-body insulin sensitivity. This finding was significant in both groups. Hence, the study put forward the therapeutic effects of weight loss on metabolic function along with an observation that the metabolic benefits of gastric bypass surgery are probably the result of weight loss alone.
Limitations:
Authors acknowledge several limitations as follow:
1) It was not a randomized trial; hence potential confounding differences between groups cannot be figured out.
2) Study might not be able to outline the unique benefits of surgery due to low statistical power and a large dropout rate.
3) Study was not adjusted for multiple testing; hence many secondary outcomes evaluated need confirmation.
4) To not exclude the possibility of different results with lesser or greater amounts of weight loss, the study assessed metabolic outcome after 16-24% weight reduction.
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