The purpose of this study was to assess the effects of a commercially available weight loss program on weight and glycemic control among obese patients with type 2 diabetes. Participants included 69 patients (49 females, 20 males) with type 2 diabetes who had a mean +/- SD age of 52.2 +/- 9.5 years, a body mass index of 39.0 +/- 6.2 kg/m(2), and hemoglobin A1c (HbA1c) of 7.5 +/- 1.6%. Over half (52.2%) of the participants were African American. Participants were randomly assigned to: 1) a portion-controlled diet (NutriSystem D) (PCD) or 2) a diabetes support and education (DSE) program. After the initial 3 months, the PCD group continued on the PCD for the remaining 3 months, and the DSE group crossed over to PCD for the remaining 3 months. The primary comparison for this study was at 3 months. At 3 months, the PCD group lost significantly more weight (7.1 +/- 4%) than the DSE group (0.4 +/- 2.3%) (P < 0.0001). From 3 to 6 months the change in weight for both groups was statistically significant. After 3 months, the PCD group had greater reductions in HbA1c than the DSE group (-0.88 +/- 1.1 vs 0.03 +/- 1.09; P < 0.001). From 3 to 6 months the PCD group had no further change in HbA1c, while the DSE group showed a significant reduction. These data suggest that obese patients with type 2 diabetes will experience significant improvements in weight, glycemic control, and cardiovascular disease risk factors after the use of a commercially available weight management program.