medwireNews: Among people with obesity and type 2 diabetes, substantial weight loss is associated with similar metabolic benefits irrespective of whether it is achieved through gastric bypass surgery or diet, suggests research published in The New England Journal of Medicine.
The cohort study included 11 patients with an average diabetes duration of 9.6 years who lost a mean 18.7% of their bodyweight following Roux-en-Y gastric bypass and 11 matched patients with similar weight loss following a low-calorie dietary intervention. Participants had an average BMI of approximately 43 kg/m2 before weight loss and 35 kg/m2 after weight loss.
Samuel Klein (Washington University School of Medicine, St Louis, Missouri, USA) and team report “considerable improvements” in body composition and metabolic response following weight loss, with “nearly identical” benefits in the surgery and diet groups.
For instance, the primary outcome of hepatic insulin sensitivity – measured by suppression of glucose production at stages 1 and 2 of a 3-stage hyperinsulinemic euglycemic pancreatic clamp procedure – improved by a mean of 7.02 μmol/kg of fat-free mass (FFM) per minute in the surgery group and by a comparable 7.04 μmol/kg FFM per minute in the diet group during clamp stage 1, and by 5.37 and 5.39 μmol/kg FFM per minute, respectively, during stage 2.
Insulin sensitivity in skeletal muscle, assessed by insulin-stimulated glucose disposal during stage 3 of the clamp procedure, as well as in adipose tissue according to suppression of lipolysis during stages 1 and 2, was also similar in the two groups, say Klein and team. They also note that beta-cell function improved following weight loss in both groups, “which appeared to be caused by an increase in beta-cell glucose sensitivity and whole-body insulin sensitivity.”
These improvements were accompanied by significant reductions in average glycated hemoglobin levels, from 7.2% (55 mmol/mol) at baseline to 6.0% (42 mmol/mol) after weight loss in the surgery group, and from 8.0% to 5.6% (64–38 mmol/mol) in the diet group. Body composition indices including fat mass, intrahepatic triglyceride content, and intraabdominal adipose tissue volume improved to a similar degree in both groups.
Klein and team say that their findings “challenge the current belief that upper gastrointestinal bypass has clinically meaningful effects on key metabolic factors involved in glucose homeostasis and the pathogenesis of diabetes that are independent of weight loss.”
Writing in an accompanying editorial, Clifford Rosen (Maine Medical Center Research Institute, Scarborough, USA) and Julie Ingelfinger (Massachusetts General Hospital, Boston, USA) caution that the study has several limitations, including small patient numbers and a nonrandomized design.
“Furthermore, all operations were Roux-en-Y procedures, so extrapolating those findings to the improved glucose tolerance associated with vertical sleeve gastrectomy, currently the most frequent procedure, must be done with caution,” they add.
Nevertheless, the editorialists believe that the research “delivers a straightforward and important message for both clinicians and patients — reducing adipose tissue volume, by whatever means, will improve blood glucose control in persons with type 2 diabetes.”
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N Engl J Med 2020; 383: 721-732
N Engl J Med 2020; 383: 777–778