People with learning disabilities are at high risk of obesity and consequent health risks. This study aimed to (1) describe levels of obesity for adults supported by learning disability services, and to (2) evaluate the effectiveness of health practitioner input with individuals with learning disabilities. Body mass index (BMI) was measured at 6 month intervals and change in BMI over time was compared between a non-input group and a group receiving practitioner input to improve healthy living. Initially 35 percent of the non-input sample was classified as clinically obese. Mean BMI increased over time for the non-input group at first, but decreased for the group that received practitioner input. The differences in weight change between the two groups reached statistical significance with a greater weight reduction in the input group. Implications for service provision are discussed.