Article - Effect of weight-maintaining ketogenic diet on glycemic control and insulin sensitivity in obese T2D subjects.

None

Take home message

In the absence of weight loss, a ketogenic diet did not improve glucose metabolism in individuals with obesity and T2D in the absence of weight loss.
However, it is unclear whether other diet types may have similar outcomes.

Evidence category

A: Meta-analyses, position-stands, randomized-controlled trials (RCTs)

Summary review

Introduction

Obesity and type 2 diabetes (T2D) are related comorbidities. Recently hypocaloric, low carbohydrate, ketogenic diets have been shown to promote weight loss and improve glycaemic control in individuals with T2D. However, it is unclear as to whether improved glucose control seen with the ketogenic diet is independent of weight loss. This study aimed to determine the effect of the ketogenic diet on glucose metabolism in individuals with T2D in the absence of weight loss.

Methods

29 overweight/obese subjects with T2D were given either 1) standard diet (SD), 2) low carbohydrate, ketogenic diet (KD) or 3) low carbohydrate, ketogenic diet with keto ester supplementation (KD+) for 10 days. All diets were designed to be weight-maintaining.
All meals were made by a certified dietitian and participants were only allowed to eat the prepared food and drink water.

Results

Body weight, fat content and body fat percentage did not change significantly in any of the groups.
The KD and KD+ diets were shown to induce metabolic changes, with carbohydrate oxidation decreasing (KD p=0.019; KD+ p=0.003) and fat oxidation increasing (KD p=0.020; KD+ p=0.002) whereas the standard diet did not.
Fasting plasma glucose modestly declined in all three groups but failed to reach significance (SD p=0.465; KD p=0.525; KD+ p=0.137).
HbA1c, insulin resistance, muscle insulin sensitivity, insulin clearance rate, diastolic blood pressure, heart rate, total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides were unchanged in all groups.

Conclusion

A weight maintaining 10-day ketogenic diet with or without ketone supplementation did not improve glucose control, insulin sensitivity, blood lipids, or blood pressure in individuals with obesity and T2D.

Clinical practice applications

Weight loss is important for improving blood sugar levels in individuals with obesity and T2D.
In the absence of weight loss, a ketogenic diet may have very little benefit for individuals who are trying to improve blood glucose control.

Considerations for future research

Future research could analyse other diets in the absence of weight loss on blood glucose levels. This would aid understanding of the level of importance of weight loss compared to diet type on blood glucose control.

Abstract

INTRODUCTION

Low carbohydrate ketogenic diets have received renewed interest for the treatment of obesity and type 2 diabetes. These diets promote weight loss, improve glycemic control, and reduce insulin resistance. However, whether the improvements in glycemic control and insulin sensitivity are secondary to the weight loss or result from a direct effect of hyperketonemia is controversial.

RESEARCH DESIGN AND METHODS

29 overweight obese subjects were randomized to one of three dietary interventions for 10 days: (1) Weight-maintaining standard diet; (2) Weight-maintaining ketogenic diet; (3) Weight-maintaining ketogenic diet plus supplementation with the ketone ester of beta-hydroxybutyrate (β-OH-B), 8 g every 8 hours. At baseline, all subjects had oral glucose tolerance test, 2-step euglycemic insulin clamp (20 mU/m.min and 60 mU/m.min) with titrated glucose and indirect calorimetry.

RESULTS

Body weight, fat content, and per cent body fat (DEXA) remained constant over the 10-day dietary intervention period in all three groups. Plasma β-OH-B concentration increased twofold, while carbohydrate oxidation decreased, and lipid oxidation increased demonstrating the expected shifts in substrate metabolism with institution of the ketogenic diet. Glucose tolerance either decreased slightly or remained unchanged in the two ketogenic diet groups. Whole body (muscle), liver, and adipose tissue sensitivity to insulin remained unchanged in all 3 groups, as did the plasma lipid profile and blood pressure.

CONCLUSION

In the absence of weight loss, a low carbohydrate ketogenic diet has no beneficial effect on glucose tolerance, insulin sensitivity, or other metabolic parameters.