The Groningen Overweight and Lifestyle (GOAL) study primarily aims at preventing weight gain by nurse practitioners (NP) guided by a standardized computerized software program. Since favourable changes in physical activity (PA) and diet may improve health independently of weight (loss), insight into effects on lifestyle habits is essential. We examined the 1-year effects of lifestyle counselling by NP on PA and diet, compared with usual care from the general practitioner (GP-UC).