This investigation will examine the effects of consuming a structured, portion-controlled, low-glycemic index diet (commercially available as the Nutrisystem-D program) on several indicators of glycemic stability and variability among participants with type 2 diabetes. Results on the portion-controlled diet will be compared with those on participants' usual diets in a randomized cross-over trial. The investigators expect that participants will exhibit greater glycemic stability (e.g., more time in euglycemic range) and less glycemic variability (e.g., smaller mean amplitude of glycemic excursions) while consuming the Nutrisystem D program, as compared with their usual diet.

This study will investigate glycemic stability and variability in response to two diets: usual diet and a commercially available portion-controlled diet. The commercially available diet will be the Nutrisystem-D program, which consists of pre-packaged meals and snacks that are supplemented with grocery items, including fruits, vegetables, and dairy items. This trial will be a randomized cross-over trial of 15 patients with type 2 diabetes (weight stable for at least 3 months prior and medication stable throughout the trial). Participants will consume each diet for a 2-week period. During each diet period, participants will wear a blinded (i.e., providing no feedback) continuous glucose monitoring (CGM) device to assess glycemic stability and variability, and will be instructed to keep a detailed record of food and beverage intake and physical activity. The two diet/assessment periods will be separated by a 1-week washout period during which no dietary instruction will be given and no outcomes will be measured. Laboratory values (HbA1c, glucose, insulin, lipid panel) and physical measures (height, weight, waist circumference, blood pressure) will be assessed at the baseline for descriptive purposes.

Primary Hypothesis: A significantly greater percentage of CGM readings will fall in the euglycemic range (71-180 mg/dl) during consumption of the Nutrisystem-D program, as compared with Usual Diet.

Secondary Hypothesis: Participants will have significantly smaller areas under the curve, mean amplitude of glycemic excurisions, mean, standard deviation, and interquartile range of glucose values, and a smaller of percentage of values in the hypo- (</= 70 mg/dl) and hyperglycemic (>180 mg/dl) ranges during consumption of the Nutrisystem-D program, as compared with Usual Diet.

Inclusion Criteria:

• Diagnosis of type 2 diabetes
• Body mass index (BMI) of 27 to 45 kg/m2
• Capacity to provide written informed consent
• Willing and committed to return for all clinic visits and complete all study-related procedures
• Men and women of all racial and ethnic groups are eligible for participation

Exclusion Criteria:

• Use of hypoglycemic medications (e.g., sulfonylureas, insulin)
• Food allergies or intolerances that would render adherence to the test diets unpleasant or unsafe
• Use of anticoagulant medications (e.g., warfarin)
• Pregnant or lactating
• More than a 5% weight gain or loss within the last 3 months
• More than one alcoholic drink per day
• Binge eating disorder
• Regular use of acetaminophen