The TREND Study: Tapered Reduction in Energy Intake as a Novel Approach to Dieting
Condition: Obesity
Study type: Interventional

Summary: 
      TREND is a pilot randomized trial comparing two alternative methods of initiating a
      low-calorie weight loss diet. The study will compare the traditional diet initiation of
      abruptly dropping energy intake to 1000 kcal/day for women and 1200 kcal/day for men versus a
      6 week tapering of energy intake from a baseline level. These two approaches will be compared
      with respect to their impact on energy regulatory systems of the body, weight loss and other
      measures, up to a year after diet initiation.
    

Detailed description: 
      Diets are the mainstay of many obesity treatment programs, yet they fail for a variety of
      reasons. Patients find it difficult to comply with caloric restriction during active weight
      loss, and to adhere to long-term changes that promote weight loss maintenance. Underlying
      these difficulties are a number of physiologic changes enacted by the body in response to
      energy restriction. These changes promote increased hunger, decreased satiety and slowed
      metabolic rate, making diet compliance and sustained weight loss very difficult. From the
      body's perspective, a rapid and substantial drop in caloric intake may represent a metabolic
      emergency, and it responds accordingly, in an attempt to maintain body weight.

      Weight loss results only from achieving and maintaining a large energy deficit, but it is not
      known whether the initiation phase of diets would be more likely to promote success if it
      were done gradually, in the form of a caloric taper. We hypothesize that, by slowly
      introducing a prescribed caloric restriction over a period of 1-2 months (rather than using
      an immediate drop in calories), the body's homeostatic response to energy restriction might
      be blunted or circumvented, resulting in lower levels of hunger, improved satiety, and better
      preservation of metabolic rate during diet initiation - all factors that would promote
      adherence and successful weight loss.

      To test this hypothesis, the investigators will conduct a pilot randomized feeding trial
      comparing two types of low-calorie diets with similar macronutrient composition. Although
      both diets will ultimately rely on similar caloric deficits to produce weight loss, they will
      differ at the point of diet initiation. The following will be compared: (1) a traditional
      diet, where the entire energy deficit is initiated immediately; and (2) a "caloric taper"
      diet, during which participants will be gradually reduced from baseline levels of energy
      consumption to the lower calorie level required for weight loss, over a 6-week period.

      After a 2-week run-in to establish equilibrium weight among 40 eligible persons, 30 obese
      adults will be randomized to the 2 study arms and follow them for 52 weeks. We will compare
      the two groups with respect to the following outcomes, measured in terms of change from
      baseline (week 0) levels:

        1. Circulating levels of the orexogenic hormone, Ghrelin, at weeks 1, 6, 12, 24, and 52;

        2. Circulating levels of the "satiety" hormones, Leptin and Glucagon-like Peptide (GLP-1)
           at weeks 1, 6, 12, 24, and 52;

        3. Body composition, as assessed with dual energy x-ray absorptiometry, at 24 and 52 weeks;

        4. Resting metabolic rate as assessed by indirect calorimetry at 24 and 52 weeks;

        5. Change in body weight (kg) and body mass index (kg/m2) at weeks 6,12, 24 and 52;

        6. Self-reported hunger (using VAS) and compliance with program at weeks 1, 6, 12, 24 and
           52.

        7. Change in weight-related quality of life, using the IWQOL-LITE at weeks 12, 24, and 52.

      Hypothesis: patients in the "taper" arm will experience less activation of body regulatory
      systems designed to oppose weight loss, with similar weight loss by 24 weeks and greater
      weight loss maintenance by 52 weeks, compared to "traditional low-calorie diet" arm patients.
    

Intervention name(s): Tapered Low Calorie Diet; Traditional Low-Calorie Diet
Intervention type(s): Behavioral; Behavioral
Intervention description(s): All participants will start with a 3 week run-in period during which they are fed a diet at 1.4 x their resting metabolic rate (kcal). Participants who are weight stable at the end of run in and are randomized to the Tapered Diet Arm will undergo the following 24 week feeding study intervention.
The difference between a participant's run-in period energy intake and low-calorie "prescribed" energy intake (1000 kcal for women; 1200kcal for men) will be divided by six. At weekly intervals from weeks 1-6, daily caloric intake will be decreased by this fixed amount, reaching the final daily caloric goal (1000 kcals for women and 1200 kcals for men) by the end of the 6th week. Participants will present twice per week during weeks 1-6 to receive food that sums to that week's prescribed calorie level.
From weeks 7-24, these participants will then follow a traditional low-calorie diet, still presenting for food pickups twice per week at a stable caloric level during this period.; All participants will start with a 3 week run-in period during which they are fed a diet at 1.4 x their resting metabolic rate (kcal). Participants who are weight stable at the end of run in and are randomized to the Traditional Diet Arm will undergo the following 24 week feeding study intervention.
Immediately following run-in, these participants will start a low-calorie diet (1000 kcal per day for women; 1200kcal for men) Participants will present twice per week during weeks 1-24 to receive food that sums to that week's prescribed calorie level.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment