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

Study Overview
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Brief Summary
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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
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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.

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

Conditions
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Overweight, Obesity, Insulin Resistance

Intervention / Treatment
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* Other: Plant-based diet
* Other: Mediterranean Diet


Participation Criteria
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Eligibility Criteria
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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

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

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


Arms and Interventions

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

What is the study measuring?
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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 |
| --- | --- | --- |
| 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 | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Cholesterol, Vegan diet, Plant-based diet, Mediterranean diet, Metabolism, Insulin sensitivity, Advanced glycation end-products