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Gastric bypass, low-calorie diet improve insulin sensitivity, secretion in diabetes patients
A very low-calorie diet improved insulin sensitivity and secretion similarly to gastric bypass in patients with type 2 diabetes, according to data presented at the 2012 Obesity Society Annual Meeting.
The study included 11 patients who underwent Roux-en-Y gastric bypass (RYGB) and 11 who began a 500 kcal per day diet (VLCD). Researchers performed intravenous glucose tests before and after initiation of surgery or diet, and also compared changes to insulin sensitivity, responses to glucose and disposition index between the groups.
At baseline, both groups had similar characteristics, including the mean duration of diabetes (5.7 years), BMI (41.4 kg/m2), fasting glucose levels (195 mg/dl) and HbA1c (8.4%). Participants lost a mean of 8.0% of their body weight over 3.4 weeks after surgery or while on the VLCD. Both groups experienced the following increases to insulin sensitivity, response to glucose and disposition index, all of which were considered statistically significant (P<.05 for all):
- Sensitivity: From 1.4 to 2.2 in the RYGB group; from 1.3 to 2.2 in the VLCD group
- Acute insulin response to glucose: From 19.8 to 86.9 in the RYGB group; from 13.0 to 84.8 in the VLCD group
- Disposition index: From 8.2 to 195.8 in the RYGB group; from 12.9 to 172.6 in the VLCD group
Differences between the two groups in degree of change were not found statistically significant for any of these factors.
“There were significant and similar improvements in glucostatic parameters after VLCD and RYGB,” the researchers concluded. “Additional subjects are currently being studied to confirm these findings.”
For more information:
Jackness CM. #32-OR: Changes in Insulin Sensitivity and Secretion in Patients With T2DM After Weight Loss Induced By Roux-en-Y Gastric Bypass or Equivalent Caloric Restriction. Presented at: the 2012 Obesity Society Annual Scientific Meeting; Sept. 20-24, San Antonio.
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The abstract 32-OR by Jackness et al. is interesting. It demonstrates similarities of insulin sensitivity and secretion in T2DM patients after 8% weight loss achieved by calorie restriction or RYGB surgery + calorie restriction with abstract analysis yielding similar insulin variables @3.4 weeks with 8% weight loss in both groups.
There have been multiple studies which show an improvement of glucostatic parameters after weight loss and gastric bypass, particularly in the early post-operative period. In contrast, weight loss by calorie restriction is a more gradual process and may not have the same degree of insulin modulation. Insulin sensitivity is known to improve with less adipose tissue. This study is intriguing as it shows similar parameters at one point in time, although longer term analysis (with an 800 kcal/d diet) has shown some differing results (Plum et al. [Obesity, Volume 19, Number 11]). It would be intriguing to monitor this effect and compare weight-loss matched insulin parameters in a prospective manner. Additionally, testing after an increase in caloric intake may be of further interest.
Glucostatic parameters may change over time, considering 1) Weight loss rate will likely differ among the two groups; 2) Historically, post-RYGB glucose homeostasis remains altered despite an increase in caloric intake (most cases); and 3) Although, in this study, insulin variables are similar at 3.4 weeks, the short-term benefits achieved at 3.4 weeks may not be durable once a higher-calorie diet is resumed. This study highlights some early changes in insulin sensitivity and secretion. Further studies will be helpful to clarify their durability and clinical significance.