Several efficacy trials and subsequent dissemination studies indicate that behavioral lifestyle interventions for diabetes risk reduction require, at a minimum, provision of 4 to 6 months of frequent intervention contact to induce clinically meaningful weight losses of at least 5% of initial body weight. Weekly contact during the first several months of intervention, followed by less frequent but regular therapeutic contact for a longer time period, appears necessary for participants to adopt and enact behavioral self-regulatory skills such as the self-monitoring of diet, weight, and physical activity and the problem solving of common physical, social, and cognitive barriers that impede sustained weight loss. In-person contact is associated with the largest effect sizes but may not be a necessary component for clinically meaningful weight loss. Regardless of intervention mode, setting, or provider, the interactive process of feedback and social support is crucial for skill development and sustained weight loss.