Rates of obesity and obesity related chronic health conditions are higher in adolescents with Intellectual and Developmental Disabilities (IDD) than those in the general population. Many of the negative health consequences observed in obese adults are already present in obese adolescents with IDD. To explore both diets and delivery systems, we completed a 2 month self-funded trial to assess the feasibility of using a technology driven system for weight management in adolescents with IDD. Twenty-two overweight/obese (BMI > 85th percentile) adolescents with mild to moderate IDD parent were randomized to a weight loss intervention using either an enhanced Stop Light Diet (enhanced with portion controlled meals (eSLD); n=11) or a Conventional Diet (CD); n=11). All participants received support from a parent. All participants received a progressive physical activity program that targeted an increase in steps ~3,000/day above baseline. Program delivery was achieved utilizing existing technology including an iPad using the FaceTimeTM application for weekly meetings and diet and physical activity was monitored using either a standard pedometer or the FitBit pedometer and Lose it! Application synced to the iPad. Twenty adolescents (11 boys, 9 girls: mean age 14.9 ( +/- 2.2) years; BMI percentile = 93.4 (+/- 6.3) percent; 30 percent minorities) completed the study. The mean weight loss at 2 months was 4.6 (+/-0.8) percent and 3.1 (+/-0.8) percent in the eSLD and CD groups, respectively. The lack of external funding prohibited a longer trial. To estimate the magnitude of weight loss that might be expected over 6 months, the time frame for weight loss in the proposed study, we assumed the rate of weight loss for months 1-2 observed in the pilot study and reduced this by 50 percent. This results in a projected weight loss at 6 months of 6.9 percent and 4.6 percent for the eSLD and CD groups, respectively. We now propose a 3 group randomized trial to evaluate the intervention delivery system and type of reduced energy diet. We will randomize 123 overweight/obese adolescents with mild to moderate IDD to one of 3 groups for an 18 month trial (6 month weight loss; 12 month weight maintenance): group 1) Face-To-Face/CD; group 2) Technology delivery/CD; group 3) Technology delivery/eSLD. All participants will receive a progressive program of physical activity. FTF will meet with a health educator and will track progress using pen and paper records for both physical activity and diet. TECH groups will receive the intervention using an iPad with the FaceTimeTM application for video meetings with a health educator and will track progress using the Lose it! application for both physical activity and diet. We will be adequately powered to compare which diet and which delivery system provides the most promising results with weight at 6 months as the primary outcome. Secondarily, we will determine if weight loss is maintained long-term (18 months) and will have extensive process analysis to determine relationships between energy balance variables, process variables, and psychosocial variables. Lastly, we will complete a cost analysis to determine if the use of technology reduces costs compared to the traditional face-to-face delivery system.