Childhood and adolescent obesity prevalence rates have steadily increased in industrialised countries in the last 20 years. Current rates of obesity range between 6 and 30%. Several studies showed that risk factors for weight gain in school age are strongly linked to low physical activity and family environmental factors (parents' education and job, number of family members, number of hours spent on watching television, etc.). In order to plan a nutritional and health educational programme, a study was conducted on the nutritional status of the school age population of the Province of Frosinone, Central Italy, and family factors that can influence it. Three percentage of the school age population of the Province of Frosinone (2053 students) and their families were randomly sampled from the Province school district database. In each of the 12 recruited schools, a meeting with teachers and students was arranged to discuss aims and methods of research and to collect informed consent by students. Each student was interviewed about physical activity, and underwent the following measurements: height, weight, bicipital, tricipital, sub-scapular and over-iliacal skinfolds, sexual development. Students' parents were asked to answer a questionnaire about family structure, parents' educational level and job, parents' height and weight, presence in the family of pathologies as hypertension or diabetes. One thousand three hundred fifty-seven students (66% of the target population) and 1802 parents (66.5% of the responders' population) agreed to enter the study. Students' age range was 8 years (11-19 years; mean age was 14.9, SD, 2.55). Among them 8.4% were considered obese, with a higher prevalence in male population (9.8%) as compared to female population (6.5%). Of these responders, 21.4% were considered at risk of overweight with no statistical difference due to gender. Statistically significant correlations of teenagers' risk of overweight and obesity with nutritional conditions of parents, mother's educational level and amount of weekly physical activity were observed. Number of children in the family, parents' age and job do not appear to be correlated to obesity or risk of overweight. Our results show that, although the prevalence of obesity in the students population in the Province of Frosinone is comparable to other Italian Provinces and lower than other industrialised countries such as USA, the percentage of students at risk of overweight is particularly high. Main risk factors for developing obesity seem to be linked to parents' nutritional conditions, mother's educational level and children's physical inactivity and this should lead to intensify efforts for preventive interventions both at family level (focused on parents) and at school.