The Lean Living Study

Sponsor

University of California, San Diego (Other)

Overall Status

Completed

CT.gov ID

NCT02501889

Collaborator

AICR Matching Grant Program (California Walnut Commission and AICR) (Other)

100

Enrollment

Location

Arms

Actual Duration (Months)

4.5

Patients Per Site Per Month

Study Details

Study Description

Brief 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.

Condition or Disease	Intervention/Treatment	Phase
Overweight and Obesity	Behavioral: Walnut-rich weight loss diet Behavioral: Standard weight loss diet	N/A

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:

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.
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.
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.

Study Design

Study Type:

Interventional

Actual Enrollment :

100 participants

Allocation:

Randomized

Intervention Model:

Parallel Assignment

Masking:

None (Open Label)

Primary Purpose:

Treatment

Official Title:

Walnut Consumption in a Weight Loss Intervention: Effects on Weight Change, Satiety and Potential Mediating Factors

Actual Study Start Date :

Aug 1, 2015

Actual Primary Completion Date :

Jun 1, 2017

Actual Study Completion Date :

Jun 1, 2017

Arms and Interventions

Arm	Intervention/Treatment
Experimental: Walnut-rich weight loss diet arm Participants will have an individualized reduced-calorie diet prescription and weight loss counseling session with the project coordinator, who is a registered dietitian. Composition of prescribed diets will be based on individual preferences. 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. All participants will have contact with the project coordinator a minimum of every 1-2 weeks. Walnuts will be provided to participants in the walnut-rich study arm.	Behavioral: Walnut-rich weight loss diet 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.
Active Comparator: Standard weight loss diet arm Participants will have an individualized reduced-calorie diet prescription and weight loss counseling session with the project coordinator, who is a registered dietitian. Composition of prescribed diets will be based on individual preferences. 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. Participants assigned to this arm will be instructed to abstain from the consumption of nuts during the study. All participants will have contact with the project coordinator a minimum of every 1-2 weeks.	Behavioral: Standard weight loss diet 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.

Arm

Intervention/Treatment

Experimental: Walnut-rich weight loss diet arm

Participants will have an individualized reduced-calorie diet prescription and weight loss counseling session with the project coordinator, who is a registered dietitian. Composition of prescribed diets will be based on individual preferences. 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. All participants will have contact with the project coordinator a minimum of every 1-2 weeks. Walnuts will be provided to participants in the walnut-rich study arm.

Behavioral: Walnut-rich weight loss diet

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.

Active Comparator: Standard weight loss diet arm

Participants will have an individualized reduced-calorie diet prescription and weight loss counseling session with the project coordinator, who is a registered dietitian. Composition of prescribed diets will be based on individual preferences. 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. Participants assigned to this arm will be instructed to abstain from the consumption of nuts during the study. All participants will have contact with the project coordinator a minimum of every 1-2 weeks.

Behavioral: Standard weight loss diet

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.

Outcome Measures

Primary Outcome Measures

Change in body weight in response to being assigned a walnut-enriched reduced-energy diet or a standard reduced-energy diet in an intensive 6-month weight loss intervention. [2 years]
Change in cardiovascular disease risk factors in response to being assigned a walnut-enriched reduced-energy diet or a standard reduced-energy diet in an intensive 6-month weight loss intervention. [2 years]

Secondary Outcome Measures

Satiety- and appetite-related visual analogue scales in response to being prescribed a walnut- enriched reduced-energy diet or a standard reduced-energy diet among the participants in the weight-loss intervention. [2 years]

Other Outcome Measures

Postprandial blood levels of satiety- and appetite-related gastrointestinal peptides (ghrelin, cholecystokinin, glucagon-like peptide, and peptide YY) following meals with or without walnuts in a sample subset, as an exploratory aim. [2 years]
Satiety- and appetite-related visual analogue scales following meals with or without walnuts in a sample subset, as an exploratory aim. [2 years]

Eligibility Criteria

Criteria

Ages Eligible for Study:

21 Years to 75 Years

Sexes Eligible for Study:

All

Accepts Healthy Volunteers:

Yes

Inclusion Criteria:

aged 21 years and older
BMI >27.0 kg/m2 and <40 kg/m2
non-smoker
willing and able to participate in clinic visits, group sessions, telephone, and internet communications at specified intervals
able to provide data through questionnaires and by telephone
willing to maintain contact with the investigators for 6 months
willing to allow blood collections
no known allergy to tree nuts
capable of performing a simple test for assessing cardiopulmonary fitness

Exclusion Criteria:

inability to participate in physical activity because of severe disability
a history or presence of a comorbid diseases for which diet modification and increased physical activity may be contraindicated
smoker
self-reported pregnancy or breastfeeding or planning a pregnancy within the next year
currently actively involved in another diet intervention study or organized weight loss program
a history or presence of a significant psychiatric disorder or any other condition that, in the investigator's judgement, would interfere with participation in the trial