Context: Prediabetes and clinical insulin resistance in adolescents are rapidly emerging clinical problems with serious health outcomes.
Objective: The objective of this study was to determine the efficacy of 2 structured lifestyle interventions, both differing in diet macronutrient composition, on insulin sensitivity.
Design: This study was a randomized controlled trial, known as Researching Effective Strategies to Improve Insulin Sensitivity in Children and Teenagers, in 2 hospitals in Sydney, Australia.
Participants: Participants included overweight or obese 10- to 17-year-olds with either prediabetes and/or clinical features of insulin resistance.
Intervention: At baseline adolescents were prescribed metformin and randomized to a structured diet, which was either high carbohydrate or moderate carbohydrate with increased protein. The program commenced with a 3-month dietary intervention, with the addition of an exercise intervention in the next 3 months.
Outcomes: The outcomes included an insulin sensitivity, anthropometry, and cardiometabolic profile at 6 months.
Results: One hundred eleven subjects (66 girls) were recruited and 98 subjects (58 girls) completed the 6-month intervention. After 3 months the mean insulin sensitivity index increased by 0.3 [95% confidence interval (CI) 0.2-0.4]. After 6 months the mean insulin (picomoles per liter) to glucose ratio (millimoles per liter) decreased by 7.2 [95%CI -12.0 to -2.3], body mass index, expressed as a percentage of the 95th centile, decreased by 9% (95% CI -3 to -15), but there was no significant change in the lipids. There were no significant differences in outcomes between the diet groups at any time point.
Conclusions: These results are in contrast with our hypothesis that adolescents randomized to the increased protein diet would have better outcomes. Further strategies are required to better address prediabetes and clinical features of insulin resistance in adolescents.