Progressive Weight Loss and Metabolic Health (PWL)

This study will evaluate the potential beneficial cardiometabolic effect of moderate (5%) weight loss and progressive (5%, 10%, and 15%) weight loss in obese adults without diabetes. Participants will be randomly assigned to one of 2 groups. Group 1: supervised weight loss group (low-calorie diet). Group 2: supervised weight maintenance group (normal diet). Of those assigned to group 1, half of the participants will lose 5% of their body weight and the other half will lose 5%, 10%, and 15% of their weight over time under the guidance of a dietitian. Research testing will be repeated at each time point (5%, 10%, and 15% weight loss). In group 2, research testing will be repeated after six months.

Half of the subjects in the weight loss arm will lose 5% of their weight through a low-calorie diet, and half will also lose 10% and 15% body weight.

Subjects in the weight maintenance arm will maintain a steady body weight (plus or minus 2% of initial body weight) for six months.

Subjects in the weight maintenance arm will maintain a steady body weight (plus or minus 2% of initial body weight) for six months.

Half of the subjects in the weight loss arm will lose 5% of their weight through a low-calorie diet, and half will also lose 10% and 15% body weight.

In the weight-loss arm we will measure insulin sensitivity at baseline, after 5% weight loss, after 10% weight loss and again after 15% weight loss. Each weight loss phase will last an average of four months for a total of approximately one year. In the weight maintenance arm we will measure insulin sensitivity at baseline and after six months.

In the weight-loss arm we will measure intra-hepatic triglyceride at baseline, after 5% weight loss, after 10% weight loss and again after 15% weight loss. Each weight loss phase will last an average of four months for a total of approximately one year. In the weight maintenance arm we will measure intra-hepatic triglyceride at baseline and after six months.

In the weight-loss arm we will measure total cholesterol at baseline, after 5% weight loss, after 10% weight loss and again after 15% weight loss. Each weight loss phase will last an average of four months for a total of approximately one year. In the weight maintenance arm we will measure total cholesterol at baseline and after six months.

In the weight-loss arm we will measure systolic blood pressure at baseline, after 5% weight loss, after 10% weight loss and again after 15% weight loss. Each weight loss phase will last an average of four months for a total of approximately one year. In the weight maintenance arm we will measure systolic blood pressure at baseline and after six months.

Colon cell proliferation rates will be determined using stable isotope labelled tracer methods in conjunction with sigmoid colon biopsy samples. In the weight-loss arm we will measure colonocyte proliferation rate at baseline, and once again after weight loss (either 5% weight loss, or 10% weight loss, or 15% weight loss; i.e. only one time after weight loss). Each weight loss phase will last an average of four months for a total of approximately one year. In the weight maintenance arm we will measure colonocyte proliferation rate at baseline and after six months.

Inclusion Criteria: Obese: Body Mass Index from 30 to 45 Insulin Resistant: HOMA-IR score greater than or equal to 2 Exclusion Criteria: diabetes smoking pregnancy breastfeeding heart failure history of liver disease including hepatitis alcoholism exercise more than 2 hours per week

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