CONTEXT: Although most health insurers exclude coverage of weight control therapy, one local insurer offered partial reimbursement of the cost of a weight control program, using an incentive plan. OBJECTIVE: To determine whether outcome-driven insurer-based reimbursement improves participation in a weight control program and short-term weight loss outcomes. DESIGN: Cohort follow-up study between January 1998 and February 2001. SETTING: Community weight management program operated by an academic medical center. SUBJECTS: Obese participants who had the potential for reimbursement (Group A, n=25) and participants in the same program classes (Group B, n=100) who had no possibility for reimbursement. Subjects in Group B were selected from among 206 potential participants using a propensity score to match them with subjects in Group A on age, gender, ethnicity, starting BMI, starting weight, and educational, economic, and demographic variables. INTERVENTION: Group lifestyle-based weight management program. The insurer reimbursed half the cost of the program to obese participants who met minimum weight criteria, paid the program fee at enrollment, attended > or =10 of the 12 classes, and lost > or =6% of initial body weight after 12 weeks. MAIN OUTCOME MEASURES: Participation rates and weight loss outcomes. RESULTS: Group A subjects attended significantly more classes (mean+/-s.d.: 10.1+/-1.8 vs 8.2+/-2.5, P<0.001) and lost more weight than Group B subjects (6.1+/-3.1 vs 3.7+/-3.6%, P=0.002). While 84% of Group A subjects attended > or =10 classes, only 37% of Group B subjects did so (P<0.001); 56% of Group A subjects lost > or =6% of body weight, but only 20% of Group B subjects did so (P<0.001); 56% of Group A subjects achieved both the class attendance and weight loss goals, but only 14% of Group B subjects did so (P<0.001). Logistic regression estimated that Group A subjects had 8.2 times the odds of attending > or =10 classes and 4.5 times the odds of losing > or =6% of body weight of Group B subjects, after controlling for class attendance. CONCLUSIONS: Insurer-based reimbursement that is contingent upon initial financial commitment on the part of the patient, consistent program participation, and successful weight loss is associated with significantly better short-term weight control outcomes.