Framingham State Food Study

This study will evaluate the effects of dietary composition on energy expenditure and chronic disease risk factors, while also exploring physiological mechanisms underlying these effects.

Many overweight and obese people can lose weight for a few months, but most have difficulty maintaining weight loss over the long term. One explanation for the poor long-term outcome of weight-loss diets relates to behavior, in that motivation to adhere to restrictive regimens typically diminishes with time. An alternative explanation is that weight loss elicits biological adaptations - specifically a decline in energy expenditure and an increase in hunger - that promote weight regain. The purpose of this study is to evaluate the effects of dietary composition on energy expenditure and risk for chronic diseases, while also exploring physiological mechanisms underlying these effects. The study will be performed in collaboration with Framingham State University, providing a novel and feasible method for feeding subjects in dining halls and monitoring compliance.

Following 12±2% weight loss on a standard run-in diet, 150 adults (aged 18 to 65 years) will be randomly assigned to one of three weight-loss maintenance diets controlled for protein content (20% of energy) and varying widely in dietary carbohydrate-to-fat ratio: Low-carbohydrate (20% of energy from carbohydrate, 60% fat), Moderate- carbohydrate (40% carbohydrate, 40% fat), High-carbohydrate (60% carbohydrate, 20% fat). During the weight-loss maintenance phase, energy intake will be adjusted to prevent changes in body weight. The primary outcome will be change in total energy expenditure (indirect calorimetry using stable isotopes) through 20 weeks. Secondary outcomes during weight maintenance will include resting energy expenditure (indirect calorimetry using respiratory gas exchange), physical activity (accelerometry), measures of insulin resistance and skeletal muscle work efficiency, components of the metabolic syndrome, and hormonal and metabolic measures that might inform an understanding of physiological mechanisms. We also will assess weight change during a 2-week ad libitum feeding phase, as an objective measure of dietary effects on hunger. The analytic framework for addressing study hypothesis will be repeated-measures analysis of variance, with adjustment for covariates (sex, race, ethnicity, age, anthropometrics, insulin sensitivity and secretion, obesity-related genes). We also will test each covariate for effect modification (covariate × diet interaction).

Eligibility Criteria:
Inclusion Criteria:

* Aged 18 to 65 years
* BMI ≥ 25 kg/m2
* Weight ≤ 425 lbs
* Medical clearance from a primary care provider
* Plans to matriculate at Framingham State University (campus-based participants: students), work on campus (campus-based participants: faculty and staff), or live in the greater Framingham area (community-based participants) throughout the academic year of enrollment in the study
* Academic and social clearance from the FSU Office of Enrollment and Student Development (student participants) or willingness to comply with Criminal Offender Record Information (CORI) check and Sex Offender Registry Information (SORI) check (community-based subjects)
* Willingness to eat and drink only the foods and beverages on the study menus during participation, with no food allergies or aversions
* Willingness to eat in the dining hall
* Willingness to abstain from consuming alcohol during participation

Exclusion Criteria:

* Change in body weight exceeding ±10% during prior year
* Recent adherence to a special diet
* Recent adherence to a vigorous physical activity regimen (e.g., participation in a varsity sport)
* Chronic use of any medication or dietary supplement that could affect study outcomes
* Current smoking (1 cigarette in the last week)
* Heavy baseline alcohol consumption (\> 10 drinks/week) or history of binge drinking (≥ 5 drinks in 1 day, anytime in past 6 months)
* Physician diagnosis of a major medical/psychiatric illness or eating disorder
* Abnormal HgA1c, TSH, BUN, creatinine; hematocrit \< 30; ALT \> 200% of normal upper limit
* Plans for a vacation during the study that would preclude adherence to prescribed diet
* Additional exclusions for female participants: Irregular menstrual cycles; any change in birth control medication during the 3 months prior to enrollment; pregnancy or lactation during the 12 months prior to enrollment