Significant weight loss among people with obesity and type 2 diabetes is associated with similar metabolic effects whether weight reduction is achieved through gastric bypass surgery or a calorie-restricted diet, suggest new data published in the New England Journal of Medicine (NEJM).
In the prospective cohort study, 11 patients with average diabetes duration of 9.6 years who underwent Roux-en-Y gastric bypass surgery and lost an average of 18.7% of their body weight were matched with 11 patients who lost a similar amount of weight following a low-calorie diet intervention. Average body mass index in both groups was approximately 43 kg/m2 before weight loss and 35 kg/m2 after weight loss.
The primary outcome measure was change in hepatic insulin sensitivity (measured by suppression of glucose production at stages 1 and 2 of a 3-stage hyperinsulinemic euglycemic pancreatic clamp procedure. Secondary outcomes were changes in muscle insulin sensitivity, beta- cell function, and 24-hour plasma glucose and insulin profiles.
Led by Mihoko Yoshino, MD, of the Washington University School of Medicine in St Louis, the research team found that weight loss was associated with:
- Improved hepatic insulin sensitivity by a mean of 7.02 μmol/kg of fat-free mass (FFM)/min in the surgery group and by a comparable 7.04 μmol/kg FFM/min in the diet group during clamp stage 1, and by 5.37 and 5.39 μmol/kg FFM/min, respectively, during stage 2. No significant differences were seen between groups.
- Increased insulin-stimulated glucose disposal, indicating insulin sensitivity in skeletal muscle, from 30.5±15.9 to 61.6±13.0 μmol/kg FFM per minute in the diet group and from 29.4±12.6 to 54.5±10.4 μmol/kg FFM/min ram of fat-free mass per minute in the surgery group; there
was no significant difference between the groups.
- Increased ß-cell function (assessed by insulin secretion relative to insulin sensitivity), by 1.83 units (95% CI, 1.22 to 2.44) in the diet group and by 1.11 units (95% CI, 0.08 to 2.15) in the surgery group, with no significant difference between the groups
In addition, the authors reported 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. Both groups also demonstrated similar improvements in body composition indices including fat mass, intrahepatic triglyceride content, and intraabdominal adipose tissue volume.
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.”
In their conclusion the authors state that the observed metabolic effects of gastric bypass surgery and calorie-restricted diet were similar and appear related to the weight loss itself “with no evident clinically important effects independent of weight loss.”
Limitations of the study include small size and absence of randomization, note NEJM associate editor Clifford Rosen, MD, and deputy editor Julie Ingelfinger, MD, in an accompanying editorial.
“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.
They add, however, 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.”