Adults with intellectual disabilities experience high rates of obesity. Despite this higher risk, there is little evidence on the effectiveness of weight-loss interventions for adults with intellectual disabilities and obesity. The present study examined the effectiveness of the TAKE 5 multi-component weight-loss intervention. Adults with obesity were invited using specialist intellectual disability services to participate in the study. Obesity was defined as a BMI of 30 kg/m2 or greater. TAKE 5 included a daily energy-deficit diet of 2510 kJ (600 kcal), achieved via a personalised dietary prescription. Participants' body weight, BMI, waist circumference and levels of physical activity and sedentary behaviour were measured before and after the intervention. A total of fifty-four individuals consented to participate, of which forty-seven (87 completed the intervention in the study period. There was a significant decrease in body weight (mean difference ? 4?47 (95 5?91, ? 3?03) kg; P less than 0?0001), BMI ( ? 1?82 (95 2?36, ? 1?29) kg/m2; P less than 0?0001), waist circumference ( ? 6?29 (95 7?85, ? 4?73) cm; P less than 0?0001) and daily sedentary behaviour of participants ( ? 41?40 (95 62?45, ? 20?35) min; P = 0?00 034). Of the participants who completed the intervention, seventeen (36?2 lost 5 is an effective weight-loss intervention for adults with intellectual disabilities and obesity. The effectiveness of TAKE 5 should be examined further in a controlled study.