Background/Objectives:To evaluate the effect of a 4.1-year (range 3-6 years) lifestyle intervention according to general public health recommendations on glucose tolerance and dropout in a Dutch population with impaired glucose tolerance (IGT).Subjects/Methods:In the Study on Lifestyle intervention and Impaired glucose tolerance Maastricht, 147 Caucasian IGT subjects were randomized to an intervention group (INT: n=74; 38 male, 36 female) and control group (CON: n=73; 37 male, 36 female). Annually, subjects underwent measurements of body weight, anthropometry, glucose tolerance (oral glucose tolerance test), insulin resistance (homeostasis model assessment-insulin resistance), maximal aerobic capacity (VO(2) max), blood lipids and blood pressure. INT received individual advice regarding a healthy diet and physical activity.Results:INT decreased their saturated fat intake, increased their carbohydrate intake (P<0.05) and VO(2) max (P=0.04) compared with CON. Body weight did not change significantly (P=0.20) between the groups. After an initial decrease, 2-h glucose levels overall increased in INT (+0.11 mmol/l), but significantly less than CON (+1.18 mmol/l; P=0.04). Diabetes incidence was lower in INT versus CON (30 versus 56%, P=0.04). Change in body weight was associated with change in 2-h glucose levels (beta=0.399 mmol/l per kg, P=0.02). Dropouts had a lower aerobic fitness and socioeconomic status, and a higher body mass index (BMI) and 2-h glucose compared with non-dropouts.Conclusions:Prolonged feasible changes in diet and physical activity prevent deterioration of glucose tolerance and reduce diabetes risk. Low socioeconomic status, low aerobic fitness and high BMI and 2-h glucose are indicative of dropout to the program.European Journal of Clinical Nutrition advance online publication, 18 May 2011; doi:10.1038/ejcn.2011.74.