Type 2 diabetes (T2D) is very prevalent and markedly increases risk for morbidity and mortality, resulting in a significant burden on individuals and the healthcare system. Thus, a major public health priority is to broadly implement prevention programs that reduce T2D onset. Three trials have found that lifestyle modification interventions that reduce body weight can significantly reduce T2D onset among individuals with prediabetes. However, these prevention programs are very intensive, requiring 35 to 47 clinical care hours delivered over 1- to 6-year periods, and cost $4804 to deliver, which has hindered broad implementation. A briefer intervention that would be less expensive would be much easier to broadly implement. Fortunately, we created a brief lifestyle modification obesity prevention program that has produced a 42% to 53% reduction in onset of overweight/obesity over 2- to 3-year follow-up in three randomized trials; the latest iteration produced a 3.66kg greater relative weight loss over 1-year follow-up compared to control participants, which is similar to the 3.4kg weight loss effect by 1-year follow-up produced by a more intensive intervention that produced a 58% reduction in future T2D onset. Theoretically, this brief intervention is more efficient because it is group-based, uses dissonance-induction to alter lifestyle behaviors that contribute to weight gain, and includes food response inhibition and attention training to devalue high-calorie foods, reduce attentional bias for high-calorie foods, and improve inhibitory control. Given that this 8-hour prevention program produced a slightly larger weight loss than a much more intensive intervention that reduced T2D onset, we propose to adapt this brief intervention to create a more cost effective T2D prevention program that would be easier to implement broadly. We propose to recruit 300 adults with prediabetes, randomize them to the novel brief T2D prevention program (Project Health T2D) or an educational control condition, and assessment them at pretest, posttest, and at 6-, 12-, 24-, and 36-month follow-up. Aim 1: Test the hypothesis that Project Health T2D will produce significantly greater reductions in body fat and T2D onset over 3-year follow-up (primary outcomes) than participants randomized to an educational video control condition. Aim 2: Test the hypothesis that reductions in body fat will mediate the effect of Project Health T2D on reductions in T2D onset over 3-year follow-up. Aim 3: Test the hypothesis that Project Health T2D will produce significantly greater reductions in blood glucose, eating disorder symptoms, depressive symptoms, and reported caloric intake, as well as greater increases in reported physical activity (secondary outcomes) over 3-year follow-up than educational video controls. Exploratory analyses will also test whether Project Health T2D is effective for both sexes, a broad range of ages and various races/ethnicities. If this trial confirms that this novel brief 8-hour prevention program significantly reduces body fat and future onset of T2D, this brief prevention program could be implemented on a much broader scale than the more intensive and costly prevention programs.