Long-term (5-Year) effects of a reduced-fat diet intervention in individuals with glucose intolerance

OBJECTIVE - To determine whether reducing dietary fat would reduce body wei ght and improve long-term glycemia in people with glucose intolerance. RESEARCH DESIGN AND METHODS - A 5-year follow-up of a 1-year randomized con trolled trial of a reduced-fat ad libitum diet versus a usual diet. Partici pants with glucose intolerance (2-h blood glucose 7.0-11.0 mmol/l) were rec ruited Ir-om a Workforce Diabetes Survey. The group that was randomized to a reduced-fat diet participated in monthly small-group education sessions o n reduced-fat eating for 1 year. Body weight and glucose tolerance were mea sured in 136 participants at baseline. 6 months, and 1 year lend of interve ntion) with follow-up at 2 years (n = 104), 3 years (n = 99), and 5 years ( n = 103). RESULTS - Compared with the control group, weight decreased in the reduced- fat-diet group (P < 0.0001); the greatest difference was noted at 1 year (- 3.3 kg), diminished at subsequent follow-up (-3.2 kg at 2 years and - 1.6 k g at 3 years), and was no longer present by 5 years (1.1 kg). Glucose toler ance also improved in patients on the reduced-fat diet: a lower proportion had type 2 diabetes or impaired glucose tolerance at 1 year (47 vs. 67%, P < 0.05), but in subsequent years, there were no differences between groups. However, the more compliant 50% of the intervention group maintained lower lasting and 2-h glucose at 5 years (P = 0.041 and P = 0.026. respectively) compared with control subjects. CONCLUSIONS - The natural history for people at high risk of developing typ e 2 diabetes 5 is weight gain and deterioration in glucose tolerance. This process ma) be ameliorated through adherence to a reduced fat intake.