OBJECTIVES:1.Dietary behavioural in an overweight and obesity population in treatment, 2.Physical activity, 3.To evaluate if the group that reaches the minimum objective(weight loss>5%), has got more life style changes. METHODS:Randomised controlled trial, 165-subjects: 70 control, 95 intervention. Weight-reduced intervention, one year follow-up: low-calorie diet, physical exercise promotion, behavioural modification techniques and health education. Variables:Sociodemography, nutrition behaviour, physical activity, anthropometry(weight-loss percentage, body mass index). Intention to treat analysis: ANOVA, ji2; SPSS 11.0. RESULTS: Age 47.1(SD12.1). In total, 82.4%Women, 53.9% very unsatisfied with the body image, 24.8% has never tried a weight-loss programme, 13.3% has tried anoretic drugs. Meal Patterns: 93.3% eats at home, 65.9% in family, 76.4% cooks herself, 65.2% eats only 2-times/day, 61.9% snacks and 54% eats binge, secret or night. Medium meal-time: 20.1 min(SD8.45). Their favourite foods: 37.6%sweets, 21.8%animal fats, 11.5%bread or flour foods, 5.5%fruit and vegetables. Smoking 25.5%, drinks no alcohol 71.8%, no exercise 61.2%. Homogeneity between control-intervention groups: without significant differences in age, sex, socioeconomic characteristics and lifestyle behaviour. There are no differences in weight measurements. Seventy-two subjects are lost(43.6%). No significant differences between the lost group and these who complete the therapy in age, sex, previous pathology, habits or weight. In the group that reaches the minimum objective, there is declining of snacking, less appetence of bingeing, secret or night eating, increasing of the daily meals and more time needed in every meal(<0.05). Increasing physical exercise during and post-treatment are associated with weight loss>5%(p<0.05). Higher intensity grade of physical activity during the diet is related with leaving obesity(p=0.00) and returning normal weight(p<0.001). People with successful outcome, experiment increasing satisfaction with the body image(p=0.00). CONCLUSIONS: 1. Nutrition behaviour in overweight and obese patients are far away of the healthy lifestyle recommendations. 2. 61.2% no exercise. 3. The improvement in life style habits produces a significant weight loss>5%.