Framingham State Food Study
Condition: Obesity; Diabetes; Cardiovascular Disease
MeSH terms: Cardiovascular Diseases
Study type: Interventional

Summary: 
      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.
    

Detailed description: 
      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).
    

Intervention name(s): Feeding study
Intervention type(s): Behavioral
Intervention description(s): Food provision throughout the study to all 3 dietary arms, with the following phases: 1) Weight loss; 2) Weight maintenance; 3) Ad libitum
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: Low carbohydrate diet; Low fat diet; Glycemic index; Weight loss maintenance