Insulin Resistance, Obesity, Overweight
Conditions
Keywords
Plant-based diet, Mediterranean diet, Vegan diet, Metabolism, Insulin sensitivity, Cholesterol, Advanced glycation end-products
Brief 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.
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.
Interventions
OTHERPlant-based diet
Weekly instructions will be given to the participants in the intervention group about following the vegan diet.
OTHERMediterranean Diet
Weekly instructions will be given to the participants in the intervention group about following the Mediterranean diet.
Sponsors
Physicians Committee for Responsible Medicine
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
TREATMENT
Masking
NONE
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
No
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
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Body weight | 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 | 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 | Change in insulin sensitivity from Baseline at 4 months | Insulin sensitivity will be assessed by the HOMA index. |
| Metabolism | 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. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| PDI, hPDI, uPDI | 16 weeks | Assess the total plant-based index (PDI), healthy PDI, and unhealthy PDI, and their relationship with weight loss. |
| Ultraprocessed foods | 16 weeks | The consumption of ultraprocessed foods will be assessed, using the NOVA classification, at baseline and 16 weeks. |
| Levels of Advanced Glycosylation Endproducts (AGEs) | Change in Advanced Glycosylation Endproducts (AGEs) from Baseline at 4 months | An AGE reader will be used to measure the Levels of the AGEs in the skin |
| Food costs | 16 weeks | Food costs will be assessed, using the U.S. Department of Agriculture Thrifty Food Plan, 2021, at baseline and 16 weeks. |
| Carbon Footprint | 16 weeks | 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. |
| Endothelial function | Change in Endothelial function from Baseline at 4 months | Endothelial function will be measured using the EndoPAT. |
| Microbiome analysis | Change in Microbiome from Baseline at 4 months | 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. |
| Dietary Advanced Glycation End Products (AGEs) | 16 weeks | Explore the effectiveness of a vegan diet in reducing dietary AGEs. |
Countries
United States
Outcome results
None listed