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Completed

NCT Number: NCT02939638

Diet, Insulin Sensitivity, and Postprandial Metabolism

This randomized, controlled trial aims to elucidate the mechanisms by which a plant-based dietary intervention causes weight loss. Using a low-fat, plant-based diet for 16 weeks, along with an untreated control for comparison, the study will measure changes in body weight, body composition, intramyocellular and/or intrahepatocellular lipid, and changes in association to body weight.

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Key information

Conditions

Overweight Body Weight Glucose Metabolism Disorders Hyperinsulinism Insulin Resistance Metabolic Diseases Nutrition Disorders Nutritional and Metabolic Diseases Obesity Overnutrition Pathological Conditions, Signs and Symptoms Signs and Symptoms

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Physicians Committee for Responsible Medicine

Washington D.C., District of Columbia, 20016, United States

About this study

In a 16-week trial, overweight adults will be randomly assigned to two groups. Changes in body weight, body composition, intramyocellular and/or intrahepatocellular lipid, and changes in association to body weight will be measured among other outcomes.

The Intervention Group will follow a low-fat, vegan diet and will receive weekly classes and support.

The Control Group will be asked to follow a conventional control diet.

This study conducts a pilot sub-study to test the hypothesis that changes in insulin sensitivity and beta-cell function observed in response to a diet intervention correlate with changes in intramyocellular and/or intrahepatocellular lipid. Another sub-study assesses the association between metabolic outcomes and gut microbiome. One additional sub-study is looking for associations between metabolic outcomes and endothelial function.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

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

Exclusion criteria

  • Diabetes mellitus, type 1 or 2, history of diabetes mellitus or 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, systemic steroids, antidepressants (tricyclics, monoamine oxidase inhibitors (MAOIs), selective serotonin reuptake inhibitors (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
  • Unstable medical or psychiatric illness
  • Evidence of an eating disorder
  • Likely to be disruptive in group sessions
  • Already following a low-fat, vegan 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

Treatment and study plan

Plant-Based Diet

Other

Weekly instructions will be given to the participants in the intervention group about following vegan diet.

Other names: Vegan diet

Control diet

Other

Participants will be asked to continue their usual diets for the 16-week study period.

Primary outcomes

  1. Body weight in kg

    Time frame: 16 weeks

    Anticipated weight-loss for intervention group compared with control group. Weight and height will be combined to report BMI in kg/m^2

  2. Fat mass in grams

    Time frame: 16 weeks

    Anticipated weight-loss for intervention group compared with control group.

  3. Visceral fat in cm^3

    Time frame: 16 weeks

    Anticipated weight-loss for intervention group compared with control group.

  4. Changes in intramyocellular and/or intrahepatocellular lipid

    Time frame: 16 Weeks

    A subset of participants will be selected for magnetic resonance (MR) spectroscopy studies quantifying hepatic lipid and/or intramyocellular and/or contents in order to provide data regarding possible causal relationships between dietary changes, ectopic lipid, and insulin sensitivity. Selected individuals with varying degrees of insulin-resistance in both groups will be assessed before and after the intervention period. These magnetic resonance spectroscopy (MRS) studies will take place at the Magnetic Research Center at Yale University School of Medicine, New Haven, CT.

  5. Insulin resistance

    Time frame: 16 weeks

    Insulin resistance will be assessed by the Homeostatic Model Assessment (HOMA) index.

  6. Resting Energy Expenditure (REE)

    Time frame: 16 weeks

    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 Metabolic Company Quark Resting Metabolic Rate (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.

  7. Postprandial metabolism

    Time frame: 16 weeks

    Participants will be asked to report to the laboratory within 60 minutes of waking and after a 12-hour fast. Postprandial metabolism will be measured for three hours after the standard meal. For premenopausal women, measures will be timed so as to occur in the luteal phase of the menstrual cycle.

Secondary outcomes

  1. Beta-cell function as measured by glucose (mmmol/L)

    Time frame: 16 weeks

    A standard meal test will be performed after an overnight fast. Plasma glucose, will be measured at 0, 30, 60, 120, and 180 min for a total of 3-hours over a 16-week period. Glucose, insulin and C-peptide will combined and analyzed to report Beta-cell function.

  2. Beta-cell function as measured by insulin (pmol/L)

    Time frame: 16 weeks

    A standard meal test will be performed after an overnight fast. Plasma insulin will be measured at 0, 30, 60, 120, and 180 min for a total of 3-hours over a 16-week period. Glucose, insulin and C-peptide will combined and analyzed to report Beta-cell function.

  3. Beta-cell function as measured by C-peptide (ng/mL)

    Time frame: 16 weeks

    A standard meal test will be performed after an overnight fast. Plasma C-peptide will be measured at 0, 30, 60, 120, and 180 min for a total of 3-hours over a 16-week period. Glucose, insulin and C-peptide will combined and analyzed to report Beta-cell function.

  4. Microbiome Analysis

    Time frame: 16 weeks

    Microbiome analysis from participant-provided stool sample. Analysis from uBiome Biotechnology company in a subset of participants. Anticipated changes in the dietary intervention group include changes in the microbiome composition that correlate with changes in insulin sensitivity.

  5. Endothelial function

    Time frame: 16 weeks

    Endothelial function will be measured using the EndoPAT, a proprietary diagnostic device for functional vascular health assessment, in a subset of participants.

  6. Diet Assessment Recall Questionnaire

    Time frame: 16 weeks

    24-hour multi-pass dietary recalls will be used to assess dietary adherence to assist study personnel in working with individuals who need additional teaching or support.

  7. The Effect of Fat Quantity & Quality on Body Composition, Insulin Resistance, & Insulin Secretion

    Time frame: 16 Weeks

    Regression Analysis will be used to assess The Effect of Fat Quantity & Quality on Body Composition, Insulin Resistance, & Insulin Secretion

  8. The Effect of Carbohydrate Quantity & Quality on Body Composition & Insulin Resistance

    Time frame: 16 Weeks

    Regression Analysis will be used to assess The Effect of Carbohydrate Quantity & Quality on Body Composition & Insulin Resistance

  9. The Effect of Protein Quantity & Quality on Body Composition, Insulin Resistance, & Insulin Secretion

    Time frame: 16 Weeks

    Regression Analysis will be used to assess The Effect of Protein Quantity & Quality on Body Composition, Insulin Resistance, & Insulin Secretion

  10. Levels of Advanced Glycosylation Endproducts (AGEs)

    Time frame: 16 Weeks

    An AGE reader will be used to measure the Levels of the AGEs in the skin

  11. Race Disparities

    Time frame: 16 weeks

    Compare the effectiveness of the vegan diet in Blacks vs. Whites in all the primary outcomes

  12. Dietary Advanced Glycation End Products (AGEs)

    Time frame: 16 weeks

    Explore the effectiveness of a vegan diet in reducing dietary AGEs.

  13. Food costs

    Time frame: 16 weeks

    Food costs will be assessed, using the U.S. Department of Agriculture Thrifty Food Plan, 2021, at baseline and 16 weeks.

  14. PDI, hPDI, uPDI

    Time frame: 16 weeks

    Assess the total plant-based index (PDI), healthy PDI, and unhealthy PDI, and their relationship with weight loss

  15. Ultraprocessed foods

    Time frame: 16 weeks

    The consumption of ultraprocessed foods will be assessed, using the NOVA classification, at baseline and 16 weeks.

Sponsors and collaborators

Lead sponsor

Physicians Committee for Responsible Medicine

Other

Collaborators

  • Yale University

Registry information

Official study title

A Randomized, Controlled Trial on Diet, Insulin Sensitivity, and Postprandial Metabolism

Acronym: TEF

Important dates

Study start
2016
Primary completion
2018
Study completion
2019
First posted
Oct 20, 2016
Registry last updated
Jul 19, 2023

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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