Improved insulin sensitivity and body composition, irrespective of macronutrient intake, after a 12 month intervention in adolescents with pre-diabetes; RESIST a randomised control trial

Abstract

Background: A higher protein to carbohydrate ratio in the diet may potentiate weight loss, improve body composition and cardiometabolic risk, including glucose homeostasis in adults. The aim of this randomised control trial was to determine the efficacy of two structured lifestyle interventions, differing in dietary macronutrient content, on insulin sensitivity and body composition in adolescents. We hypothesised that a moderate-carbohydrate (40-45% of energy), increased-protein (25-30%) diet would be more effective than a high-carbohydrate diet (55-60%), moderate-protein (15%) diet in improving outcomes in obese, insulin resistant adolescents.

Methods: Obese 10-17 year olds with either pre-diabetes and/or clinical features of insulin resistance were recruited at two hospitals in Sydney, Australia. At baseline adolescents were prescribed metformin and randomised to one of two energy restricted diets. The intervention included regular contact with the dietician and a supervised physical activity program. Outcomes included insulin sensitivity index measured by an oral glucose tolerance test and body composition measured by dual-energy x-ray absorptiometry at 12 months.

Results: Of the 111 adolescents recruited, 85 (77%) completed the intervention. BMI expressed as a percentage of the 95th percentile decreased by 6.8% [95% CI: -8.8 to -4.9], ISI increased by 0.2 [95% CI: 0.06 to 0.39] and percent body fat decreased by 2.4% [95% CI: -3.4 to -1.3]. There were no significant differences in outcomes between diet groups at any time.

Conclusion: When treated with metformin and an exercise program, a structured, reduced energy diet, which is either high-carbohydrate or moderate-carbohydrate with increased-protein, can achieve clinically significant improvements in obese adolescents at risk of type 2 diabetes.

Trial registration: Australian New Zealand Clinical Trail Registry ACTRN12608000416392 . Registered 25 August 2008.

Figure 1

RESIST participant flow.

Figure 2

Glycemic status and body composition measures by dietary group over the 12 month intervention. Estimated marginal means (SE) are presented from linear mixed models for the moderate-carbohydrate, increased-protein diet group (▼) and the high-carbohydrate diet group (△). a: Insulin sensitivity index. ¹Significance between baseline and 3 months and 12 months as indicated. ²Significance between 3 and 12 months. b: Total body fat percent measured by dual energy x-ray absorptiometry (Fat % DXA). ¹Significance between baseline and 3 months and 12 months as indicated. ²Significance between 3 and 12 months. c: Fat free mass index. ¹Significance between baseline and 3 months and 12 months as indicated. ²Significance between 3 and 12 months. d: BMI%95th centile. ¹Significance between baseline and 3 months, 6 months and 12 months as indicated. ³Significance between 3 and 6 months. ⁴Significance between 6 and 12 months.