OverweightNCT03698955
Low-Fat Vegan Diet Versus a Mediterranean Diet on Body Weight
A study testing Plant-based diet and Mediterranean Diet in people with Overweight and Obesity, run by Physicians Committee for Responsible Medicine at 1 site in United States.
Trial summary
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. Read more about this study
- Who is it for?
- Ages 18 years and older
- Conditions the study is for
- Overweight, Obesity, Insulin Resistance
- What is being tested?
- Plant-based diet and Mediterranean Diet
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 62 participants
- Where
- 1 siteUnited States
- Study dates
- 22 Oct 2018to 13 Nov 2019
- Phase
- Interventional
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Men and women age ≥18 years of age
- Body mass index 28-40 kg/m2
Who cannot join
- 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
Show all 13Show fewer
- 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
Trial locations and contacts
1 site in 1 country.
United States1 site
Physicians Committee for Responsible Medicine
Washington D.C., District of Columbia, 20016
About this study
Official title: 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.
Read the 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.
- Conditions
- Overweight, Obesity, Insulin Resistance
- Being tested
- Plant-based diet, Mediterranean Diet
- Keywords
- Plant-based diet, Mediterranean diet, Vegan diet, Metabolism, Insulin sensitivity, Cholesterol, Advanced glycation end-products
- Medical subject headings
- Overweight, Obesity, Insulin Resistance
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Plant-based dietOther
Also called Vegan diet
Weekly instructions will be given to the participants in the intervention group about following the vegan diet.
Mediterranean DietOther
Weekly instructions will be given to the participants in the intervention group about following the Mediterranean diet.
| Study group | Role | What they receive |
|---|---|---|
| Plant-based diet | Active comparator | The diet group will be asked to follow a low-fat, vegan diet for 16 weeks. Receives: Other: Plant-based diet |
| Mediterranean diet | Active comparator | The diet group will be asked to follow a Mediterranean diet for 16 weeks. Receives: Other: Mediterranean Diet |
What is being measured
The primary outcome is the main question the study is designed to answer.
Body weight
Body weight will be assessed at the baseline and at the completion of both interventions.
Measured: Change in body weight from Baseline at 4 months
Plasma lipids
Plasma cholesterol, triglycerides, and HbA1c will be measured in a fasting state.
Measured: Change in plasma cholesterol, triglycerides, and HbA1c from Baseline at 4 months
Insulin sensitivity
Insulin sensitivity will be assessed by the HOMA index.
Measured: 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.
Measured: Changes in metabolism from Baseline at 4 months
Secondary outcomes (8)
Levels of Advanced Glycosylation Endproducts (AGEs)
An AGE reader will be used to measure the Levels of the AGEs in the skin
Measured: Change in Advanced Glycosylation Endproducts (AGEs) from Baseline at 4 months
Endothelial function
Endothelial function will be measured using the EndoPAT.
Measured: 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.
Measured: Change in Microbiome from Baseline at 4 months
Dietary Advanced Glycation End Products (AGEs)
Explore the effectiveness of a vegan diet in reducing dietary AGEs.
Measured: 16 weeks
PDI, hPDI, uPDI
Assess the total plant-based index (PDI), healthy PDI, and unhealthy PDI, and their relationship with weight loss.
Measured: 16 weeks
Ultraprocessed foods
The consumption of ultraprocessed foods will be assessed, using the NOVA classification, at baseline and 16 weeks.
Measured: 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.
Measured: 16 weeks
Food costs
Food costs will be assessed, using the U.S. Department of Agriculture Thrifty Food Plan, 2021, at baseline and 16 weeks.
Measured: 16 weeks
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted9 Oct 2018
- Study start22 Oct 2018
- Primary completion13 Nov 2019
- Study completion13 Nov 2019
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (7)Papers the sponsor has linked to this study.
- Other trials for OverweightStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- None (open label)
- Enrolment
- 62 participants (actual)
Sponsor and investigators
- Lead sponsor
- Physicians Committee for Responsible Medicine
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
- Investigators
- Neal Barnard, Principal investigator, Physicians Committee for Responsible Medicine
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT03698955
- Sponsor's protocol ID
- Pro00029777
- Status last verified
- Feb 2024
- First submitted
- 3 Oct 2018
- Last updated
- 27 Sep 2024
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Undecided
Publications
Kahleova H, Znayenko-Miller T, Jayaraman A, Chiavaroli L, Holubkov R, Barnard ND. Animal vs plant-based processed foods have different effects on body weight: a secondary analysis of a randomized, cross-over trial. Nutr Res. 2026 Oct 1;155:142-147. doi: 10.1016/j.nutres.2026.09.010. Online ahead of print.
PubMed 42913060Jayaraman A, McKay B, Chiavaroli L, Back S, Fischer I, Smith R, Holubkov R, Barnard ND, Kahleova H. Environmental footprint of a low-fat vegan diet and Mediterranean diet: a secondary analysis of a randomised clinical trial. BMJ Nutr Prev Health. 2026 Apr 30;9(1):e001482. doi: 10.1136/bmjnph-2025-001482. eCollection 2026.
PubMed 42540154Kahleova H, Smith R, Fischer I, Brennan H, Znayenko-Miller T, Holubkov R, Barnard ND. Plant-based dietary index on the Mediterranean and a vegan diet: a secondary analysis of a randomized, cross-over trial. Front Nutr. 2025 Nov 19;12:1666807. doi: 10.3389/fnut.2025.1666807. eCollection 2025.
PubMed 41346691Kahleova H, Maracine C, Himmelfarb J, Jayaraman A, Znayenko-Miller T, Holubkov R, Barnard ND. Dietary acid load on the Mediterranean and a vegan diet: a secondary analysis of a randomized, cross-over trial. Front Nutr. 2025 Jun 25;12:1634215. doi: 10.3389/fnut.2025.1634215. eCollection 2025.
PubMed 40635898Kahleova H, Znayenko-Miller T, Motoa G, Eng E, Prevost A, Uribarri J, Holubkov R, Barnard ND. Dietary advanced glycation end-products and their associations with body weight on a Mediterranean diet and low-fat vegan diet: a randomized, cross-over trial. Front Nutr. 2024 Aug 8;11:1426642. doi: 10.3389/fnut.2024.1426642. eCollection 2024.
PubMed 39176029Kahleova 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.
PubMed 34330460Barnard 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.
PubMed 33544066
Study at a glance
From the registry record, last updated by the sponsor on 27 Sep 2024. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A Randomized, Cross-Over Trial on the Effects of a Low-Fat Vegan Diet Versus a Mediterranean Diet on Body Weight
- ClinicalTrials.gov ID
- NCT03698955
- Acronym / sponsor ID
- Pro00029777
- Conditions
- Overweight, Obesity, Insulin Resistance
- Keywords
- Plant-based diet, Mediterranean diet, Vegan diet, Metabolism, Insulin sensitivity, Cholesterol, Advanced glycation end-products
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 62 participants (actual)
- Lead sponsor
- Physicians Committee for Responsible MedicineUniversity, hospital or other
- Study start
- 22 Oct 2018 (actual)
- Primary completion
- 13 Nov 2019 (actual)
- Study completion
- 13 Nov 2019 (actual)
- First posted
- 9 Oct 2018 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
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 design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- None (open label)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Plant-based diet | Active comparator | Other: Plant-based dietThe diet group will be asked to follow a low-fat, vegan diet for 16 weeks. |
| Mediterranean diet | Active comparator | Other: Mediterranean DietThe diet group will be asked to follow a Mediterranean diet for 16 weeks. |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (2 listed)
- Men and women age ≥18 years of age
- Body mass index 28-40 kg/m2
Key exclusion criteria (13 listed)
- 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
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Plant-based dietAlso: Vegan dietWeekly instructions will be given to the participants in the intervention group about following the vegan diet. | Other | Plant-based diet |
| Mediterranean DietWeekly instructions will be given to the participants in the intervention group about following the Mediterranean diet. | Other | Mediterranean diet |
Primary outcome
Body weight
Time frame: Change in body weight from Baseline at 4 months
Body weight will be assessed at the baseline and at the completion of both interventions.
Plasma lipids
Time frame: Change in plasma cholesterol, triglycerides, and HbA1c from Baseline at 4 months
Plasma cholesterol, triglycerides, and HbA1c will be measured in a fasting state.
Insulin sensitivity
Time frame: Change in insulin sensitivity from Baseline at 4 months
Insulin sensitivity will be assessed by the HOMA index.
Metabolism
Time frame: Changes in metabolism from Baseline at 4 months
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.
8 secondary outcomes
Levels of Advanced Glycosylation Endproducts (AGEs)
Time frame: Change in Advanced Glycosylation Endproducts (AGEs) from Baseline at 4 months
Endothelial function
Time frame: Change in Endothelial function from Baseline at 4 months
Microbiome analysis
Time frame: Change in Microbiome from Baseline at 4 months
Dietary Advanced Glycation End Products (AGEs)
Time frame: 16 weeks
PDI, hPDI, uPDI
Time frame: 16 weeks
Ultraprocessed foods
Time frame: 16 weeks
Carbon Footprint
Time frame: 16 weeks
Food costs
Time frame: 16 weeks
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 27 Sep 2024.
- Derived from this study: PubMed 42913060Kahleova H, Znayenko-Miller T, Jayaraman A, Chiavaroli L, Holubkov R, Barnard ND. Animal vs plant-based processed foods have different effects on body weight: a secondary analysis of a randomized, cross-over trial. Nutr Res. 2026 Oct 1;155:142-147. doi: 10.1016/j.nutres.2026.09.010. Online ahead of print.
- Derived from this study: PubMed 42540154Jayaraman A, McKay B, Chiavaroli L, Back S, Fischer I, Smith R, Holubkov R, Barnard ND, Kahleova H. Environmental footprint of a low-fat vegan diet and Mediterranean diet: a secondary analysis of a randomised clinical trial. BMJ Nutr Prev Health. 2026 Apr 30;9(1):e001482. doi: 10.1136/bmjnph-2025-001482. eCollection 2026.
- Derived from this study: PubMed 41346691Kahleova H, Smith R, Fischer I, Brennan H, Znayenko-Miller T, Holubkov R, Barnard ND. Plant-based dietary index on the Mediterranean and a vegan diet: a secondary analysis of a randomized, cross-over trial. Front Nutr. 2025 Nov 19;12:1666807. doi: 10.3389/fnut.2025.1666807. eCollection 2025.
- Derived from this study: PubMed 40635898Kahleova H, Maracine C, Himmelfarb J, Jayaraman A, Znayenko-Miller T, Holubkov R, Barnard ND. Dietary acid load on the Mediterranean and a vegan diet: a secondary analysis of a randomized, cross-over trial. Front Nutr. 2025 Jun 25;12:1634215. doi: 10.3389/fnut.2025.1634215. eCollection 2025.
- Derived from this study: PubMed 39176029Kahleova H, Znayenko-Miller T, Motoa G, Eng E, Prevost A, Uribarri J, Holubkov R, Barnard ND. Dietary advanced glycation end-products and their associations with body weight on a Mediterranean diet and low-fat vegan diet: a randomized, cross-over trial. Front Nutr. 2024 Aug 8;11:1426642. doi: 10.3389/fnut.2024.1426642. eCollection 2024.
- Derived from this study: PubMed 34330460Kahleova 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.
- Derived from this study: PubMed 33544066Barnard 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.
- Individual participant dataSharing planned: Undecided
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Neal Barnard principal investigator
Physicians Committee for Responsible Medicine
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Plant-based diet and Mediterranean Diet in people with Overweight and Obesity, run by Physicians Committee for Responsible Medicine at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 2 inclusion and 13 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 27 Sep 2024. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Body weight (time frame: Change in body weight from Baseline at 4 months). The study lists 4 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT03698955, which also lists 7 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 27 Sep 2024; AzTrials last refreshed its copy on 7 Nov 2026.