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

Abstract

OBJECTIVE - To determine whether reducing dietary fat would reduce body weight and improve long-term glycemia in people with glucose intolerance. RESEARCH DESIGN AND METHODS - A 5-year follow-up of a 1-year randomized controlled trial of a reduced-fat ad libitum diet versus a usual diet. Participants with glucose intolerance (2-h blood glucose 7.0-11.0 mmol/l) were recruited from a Workforce Diabetes Survey. The group that was randomized to a reduced-fat diet participated in monthly smallgroup education sessions on reduced-fat eating for 1 year. Body weight and glucose tolerance were measured in 1.36 participants at baseline, 6 months, and 1 year (end of intervention), 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 kg at 3 years), and was no longer present by 5 years (1.1 kg). Glucose tolerance 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 fasting 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 type 2 diabetes is weight gain and deterioration in glucose tolerance. This process may be ameliorated through adherence to a reduced fat intake.