OBJECTIVE We reported previously that low-saturated-fat dietary counseling started in infancy improves insulin sensitivity in healthy children 9 years of age. The aim of this study was to evaluate the effect of life-long dietary counseling on insulin sensitivity in healthy adolescents between 15 and 20 years of age. In addition, we examined dietary fiber intake and the polyunsaturated fatty acid (PUFA) + monounsaturated (MUFA)-to-saturated fatty acid (SFA) ratio in the intervention and control adolescents and the association of these dietary factors with homeostasis model of insulin resistance (HOMA-IR).

RESEARCH DESIGN AND METHODS The study comprised adolescents participating in the randomized, controlled Special Turku Coronary Risk Factor Intervention Project (STRIP) study, which aims to guide the study participants toward a diet beneficial for cardiovascular health. HOMA-IR was assessed annually between 15 and 20 years of age (n = 518; intervention, n = 245; control, n = 273), along with diet, BMI, pubertal status, serum cotinine concentrations, and physical activity. Dietary counseling was given biannually during the follow-up.

RESULTS HOMA-IR was lower (7.5% on average) in the intervention group than in the control group between 15 and 20 years of age (P = 0.0051). The intervention effect was similar in girls and boys. The PUFA+MUFA-to-SFA ratio was higher (P < 0.0001) and the dietary fiber (g/MJ) intake was higher (P = 0.0058) in the intervention group compared with the control group. There was no association between the PUFA+MUFA-to-/SFA ratio and HOMA-IR, whereas dietary fiber intake (g/MJ) was associated with HOMA-IR in girls (P < 0.0001).

CONCLUSIONS Dietary counseling initiated in infancy and maintained until 20 years of age was associated with improved insulin sensitivity in adolescents.