Low-Fat Vegan Diet Versus a Mediterranean Diet on Body Weight

A Randomized, Cross-Over Trial on the Effects of a Low-Fat Vegan Diet Versus a Mediterranean Diet on Body Weight

This randomized, cross-over trial aims to assess changes in body weight, plasma lipids, insulin sensitivity, and postprandial metabolism with a low-fat, plant-based diet and a Mediterranean diet, both followed for 4 months.

Study Overview

• Status: Completed
• Conditions: Obesity; Overweight; Insulin Resistance
• Intervention / Treatment: Other: Plant-based diet; Other: Mediterranean Diet

Detailed Description

In a 36-week cross-over trial, overweight adults will consume a low-fat vegan diet and a Mediterranean diet in two separate 16-week phases. Changes in body weight will be the primary dependent variable. In addition, plasma lipid concentrations, insulin sensitivity, and postprandial metabolism will also be assessed and changes over time will be compared between the two diets.

Participants will be randomly assigned to start either a low-fat vegan diet or a Mediterranean diet for 16 weeks. Both groups will receive weekly classes and support, and will be asked to make no changes to their exercise patterns for the study period. After a 4-week washout period, participants will cross over to the second dietary intervention for another 16 weeks.

• Study Type: Interventional
• Enrollment (Actual): 62
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • District of Columbia
    • Washington, District of Columbia, United States, 20016
      • Physicians Committee for Responsible Medicine

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Men and women age ≥18 years of age
• Body mass index 28-40 kg/m2

Exclusion Criteria:

• Diabetes mellitus type 1, history of any endocrine condition that would affect body weight, such as thyroid disease, pituitary abnormality, or Cushing's syndrome
• Smoking during the past six months
• Alcohol consumption of more than 2 drinks per day or the equivalent, episodic increased drinking (e.g., more than 2 drinks per day on weekends), or a history of alcohol abuse or dependency followed by any current use
• Use of recreational drugs in the past 6 months
• Use within the preceding six months of medications that affect appetite or body weight, such as estrogens or other hormones, thyroid medications (unstable dose within the preceding 6 months), systemic steroids, antidepressants (tricyclics, MAOIs, SSRIs), antipsychotics, lithium, anticonvulsants, appetite suppressants or other weight-loss drugs, herbs for weight loss or mood, St. John's wort, ephedra, beta blockers
• Pregnancy or intention to become pregnant during the study period, as verified by self--- - Unstable medical or psychiatric illness
• Evidence of an eating disorder
• Likely to be disruptive in group sessions
• Already following a low-fat vegan diet or Mediterranean diet
• Lack of English fluency
• Inability to maintain current medication regimen
• Inability or unwillingness to participate in all components of the study
• Intention to follow another weight-loss method during the trial

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Plant-based diet; The diet group will be asked to follow a low-fat, vegan diet for 16 weeks.	Other: Plant-based diet; Weekly instructions will be given to the participants in the intervention group about following the vegan diet.; Other Names: Vegan diet
Active Comparator: Mediterranean diet; The diet group will be asked to follow a Mediterranean diet for 16 weeks.	Other: Mediterranean Diet; Weekly instructions will be given to the participants in the intervention group about following the Mediterranean diet.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Body weight	Body weight will be assessed at the baseline and at the completion of both interventions.	Change in body weight from Baseline at 4 months
Plasma lipids	Plasma cholesterol, triglycerides, and HbA1c will be measured in a fasting state.	Change in plasma cholesterol, triglycerides, and HbA1c from Baseline at 4 months
Insulin sensitivity	Insulin sensitivity will be assessed by the HOMA index.	Change in insulin sensitivity from Baseline at 4 months
Metabolism	Participants will be asked to report to the laboratory within 60 minutes of waking and after a 12-hour fast. Following 30 minutes of quiet rest in a dimly lit room, pulse, respiratory rate, and body temperature will be measured. REE will be measured for 20 minutes through indirect calorimetry (Cosmed Quark RMR, Chicago, IL) utilizing a ventilated hood system. The laboratory temperature will be maintained at 23 degrees C throughout, and precautions will be taken to minimize any disturbances that could affect the metabolic rate. For premenopausal women, measures will be timed so as to occur in the luteal phase of the menstrual cycle. Postprandial metabolism will be measured for three hours after the standard meal.	Changes in metabolism from Baseline at 4 months

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Dietary Advanced Glycation End Products (AGEs)	Explore the effectiveness of a vegan diet in reducing dietary AGEs.	16 weeks
Levels of Advanced Glycosylation Endproducts (AGEs)	An AGE reader will be used to measure the Levels of the AGEs in the skin	Change in Advanced Glycosylation Endproducts (AGEs) from Baseline at 4 months
Endothelial function	Endothelial function will be measured using the EndoPAT.	Change in Endothelial function from Baseline at 4 months
Microbiome analysis	Microbiome analysis will be performed from participant-provided stool sample. Anticipated changes in the dietary intervention group include changes in the microbiome composition that correlate with changes in insulin sensitivity.	Change in Microbiome from Baseline at 4 months
Ultraprocessed foods	The consumption of ultraprocessed foods will be assessed, using the NOVA classification, at baseline and 16 weeks.	16 weeks
PDI, hPDI, uPDI	Assess the total plant-based index (PDI), healthy PDI, and unhealthy PDI, and their relationship with weight loss.	16 weeks
Carbon Footprint	The greenhouse gas emissions (GHGE) and cumulative energy demand (CED) will be assessed, using the database of Food Impacts on the Environment for Linking to Diets (dataFIELD) and What We Eat In America (WWEIA) database, at baseline and 16 weeks.	16 weeks

Collaborators and Investigators

• Sponsor: Physicians Committee for Responsible Medicine
• Investigators: Principal Investigator: Neal Barnard, Physicians Committee for Responsible Medicine

Publications and helpful links

General Publications

• Kahleova H, McCann J, Alwarith J, Rembert E, Tura A, Holubkov R, Barnard ND. A plant-based diet in overweight adults in a 16-week randomized clinical trial: The role of dietary acid load. Clin Nutr ESPEN. 2021 Aug;44:150-158. doi: 10.1016/j.clnesp.2021.05.015. Epub 2021 May 29.
• Barnard ND, Alwarith J, Rembert E, Brandon L, Nguyen M, Goergen A, Horne T, do Nascimento GF, Lakkadi K, Tura A, Holubkov R, Kahleova H. A Mediterranean Diet and Low-Fat Vegan Diet to Improve Body Weight and Cardiometabolic Risk Factors: A Randomized, Cross-over Trial. J Am Nutr Assoc. 2022 Feb;41(2):127-139. doi: 10.1080/07315724.2020.1869625. Epub 2021 Feb 5.

Study record dates

Study Major Dates

• Study Start (Actual): October 22, 2018
• Primary Completion (Actual): November 13, 2019
• Study Completion (Actual): November 13, 2019

Study Registration Dates

• First Submitted: October 3, 2018
• First Submitted That Met QC Criteria: October 4, 2018
• First Posted (Actual): October 9, 2018

Study Record Updates

• Last Update Posted (Actual): February 20, 2024
• Last Update Submitted That Met QC Criteria: February 16, 2024
• Last Verified: February 1, 2024

More Information

Terms related to this study

• Keywords: Cholesterol; Insulin sensitivity; Metabolism; Mediterranean diet; Plant-based diet; Advanced glycation end-products; Vegan diet
• Additional Relevant MeSH Terms: Glucose Metabolism Disorders; Metabolic Diseases; Overnutrition; Nutrition Disorders; Hyperinsulinism; Insulin Resistance; Overweight; Body Weight
• Other Study ID Numbers: Pro00029777

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No