The Lean Living Study
Condition: Overweight and Obesity
MeSH terms: Overweight
Study type: Interventional

Summary: 
      This study investigates whether walnuts help to promote weight loss, associated with
      increased meal satiety and satisfaction, in 100 overweight and obese men and women who are
      participating in a 6-month behavioral weight loss intervention. Participants will be randomly
      assigned to a walnut-enriched reduced-calorie diet or a standard reduced-calorie diet. Body
      weight, risk factors for cardiovascular disease, and self-reported feelings relevant to
      satiety and appetite will be measured at baseline and 3- and 6-month follow-up. Also, the
      response of gastrointestinal tract hormones following meals with or without walnuts will be
      measured in a subset of study participants (n=20). Results from this study will contribute to
      understanding the role of nuts in weight control, including further knowledge of the
      mechanisms, and will expand knowledge of how nuts in the diet may contribute to the
      prevention and management of obesity.
    

Detailed description: 
      Epidemiological studies have linked regular consumption of nuts with lower body mass index
      and reduced likelihood of weight gain in adulthood. Several mechanisms have been proposed to
      explain why nuts may facilitate weight management, including their high satiety property
      which may promote dietary compensation with reduced subsequent energy intake. Although
      proposed as a possible mediating factor, satiety and satiation in relation to nuts or
      nut-containing meals have been examined in only a few previous studies. The effects of nut
      consumption in the context of a weight loss intervention have been examined in only five
      previously-published randomized studies, which have tested the effects of almonds, pistachios
      or peanuts (but not walnuts) and have had mixed results.

      This project is a study to investigate the effects of a walnut-enriched vs. standard
      reduced-energy diet on body weight and satiety via pre- and post-meal ratings scales, as well
      as exploring the response of satiety- and appetite-related gastrointestinal peptides to meals
      with or without walnuts in a sample subset.

      The specific aims of this study are:

        1. To compare the effects of a walnut-enriched reduced-energy diet to a standard
           reduced-energy diet on body weight and cardiovascular disease risk factors in a sample
           of overweight and obese adults in an intensive 6-month weight loss intervention.

        2. To examine whether there is a differential response in satiety- and appetite-related
           ratings scales in association with a walnut-enriched reduced-energy diet and a standard
           reduced-energy diet among the participants in this weight-loss study.

        3. To examine the response of satiety- and appetite-related gastrointestinal peptides
           (ghrelin, cholecystokinin, glucagon-like peptide, and peptide YY), to meals with or
           without walnuts in a sample subset, as an exploratory aim.

      The first two aims will be addressed in a randomized controlled study involving 100
      overweight or obese men and women assigned to a walnut-enriched reduced-energy diet or a
      standard reduced-energy diet in the context of a 6-month intensive weight loss intervention.
      Subjective satiety- and appetite-related ratings will be collected at specific intervals
      before lunch and dinner using visual analogue scales. Postprandial gastrointestinal peptide
      response to a meal with or without walnuts, the third and exploratory aim, will be measured
      in a subset of study participants (n=20) using a within-subject crossover study design.

      The investigators hypothesize that participants assigned to the walnut-enriched diet study
      arm will have greater weight loss and overall better improvements in cardiovascular disease
      risk factors, and that ratings of hunger, fullness, and anticipated prospective consumption
      will differ from those of participants assigned to the standard reduced-energy diet. The
      investigators hypothesize that postprandial satiety- and appetite-related gastrointestinal
      peptides, which play a role in short-term control of appetite and may be biomarkers of
      satiety, may differ in response to different isocaloric meal composition. Results from this
      study will contribute to understanding the role of nuts in weight control, including further
      knowledge of the explanatory mechanisms, and will expand knowledge of how nuts in the diet
      may contribute to the prevention and management of obesity.
    

Intervention name(s): Walnut-rich weight loss diet; Standard weight loss diet
Intervention type(s): Behavioral; Behavioral
Intervention description(s): Composition of prescribed diets will be based on individual preferences, with the goal of reduced energy intake and increased energy expenditure. During the 6-month intervention, study subjects will participate in individualized counseling and group sessions, with in-person, telephone, email and text message contacts to provide support and behavioral guidance and strategies. Walnuts will be provided to participants. The overall content of the intervention consists of key elements of cognitive-behavioral therapy for obesity. The physical activity component emphasizes planned aerobic exercise, increased physical activity in the lifestyle, and strength training.; Composition of prescribed diets will be based on individual preferences, with the goal of reduced energy intake and increased energy expenditure. During the 6-month intervention, study subjects will participate in individualized counseling and group sessions, with in-person, telephone, email and text message contacts to provide support and behavioral guidance and strategies. The overall content of the intervention consists of key elements of cognitive-behavioral therapy for obesity. The physical activity component emphasizes planned aerobic exercise, increased physical activity in the lifestyle, and strength training.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: obesity; overweight; weight loss; satiety; walnuts; gastrointestinal peptides