The purpose of this study is to determine whether a low-fat or low-glycemic load diet is more effective for controlling weight and blood glucose in persons with type 2 diabetes.

This research is a randomized controlled trial to compare long-term outcomes behavioral weight loss interventions that include either low-fat or low-glycemic load dietary instruction. Targets for energy intake and expenditure, and behavioral skills taught, are identical across the two diets. Additionally, both treatments include 20 weekly group sessions, followed by 10 every-other-week sessions. Participants are overweight and obese adults with type 2 diabetes. The primary outcomes are changes in weight and glycated hemoglobin. Those randomized to the low-glycemic load diet are expected to achieve greater weight losses and maintain better glycemic control at the end of treatment (i.e., week 40) and after 1 year of no-treatment follow-up (i.e., week 92).

Inclusion Criteria:

• Type 2 Diabetes Mellitus
• Body mass index (BMI) of 27 to 45 kg/m2 with weight </= 136 kg (300 lbs.
• Capacity to provide written informed consent
• Systolic blood pressure between 90 and 160 mm Hg, inclusive.
• Diastolic blood pressure between 65 and 100 mm Hg, inclusive.
• Resting heart rate between 65 and 90 beats per minute, inclusive.

Exclusion Criteria:

• a recent (i.e., within 1 year) myocardial infarction
• unstable angina
• malignant arrhythmias
• history of cerebrovascular, renal, or hepatic disease
• history of seizures
• protein wasting diseases (e.g., Cushing's syndrome)
• uncontrolled hypertension (> 160/100 mm Hg)
• type 1 diabetes
• uncontrolled thyroid disease
• pregnancy or lactation
• electrolyte abnormalities
• clinically significant psychosocial impairment (principally, major depression)
• treatment with steroids