Intellectually disabled (ID) people are at high risk of overweight and obesity. Prevalence and risk factors were assessed in a French population of ID adults attending specialized institutions, using a questionnaire focusing on demographic characteristics, physical activities, food habits and self-awareness about body and health. Data analysis included descriptive statistics, univariate and multivariate regression. Overall, 570 participants were included in the analysis (59% male), aged 19-59 years. The mean body mass index (BMI) was 24.9 kg/m(2); 45.6% of participants were overweight (BMI ≥ 25), including 17.2% who were obese (BMI ≥ 30). Participants practiced sports for 5.7h/week on average and were sedentary for 21.8h/week (time spent in front of some kind of screen). Most participants had food and self-care habits usually regarded as healthy. Eighty percent of them felt unhappy with their body and their physical capacities, but otherwise expressed a rather good opinion of themselves. Bivariate and multivariate analyses showed that some behavioral habits were associated with a reduced incidence of overweight and/or obesity, such as regular sport practice outside the institution, good personal body care or alcohol avoidance. The strongest risk factor was gender. Women were much more at risk than men of being overweight (53.9% versus 39.9%) and obese (28.2% versus 9.5%). Results suggest numerous ways to improve the health of institutionalized ID adults, related to sports education, nutrition and self-care, with particular attention paid to women.