Vitis Intervention Trial in Substrate Metabolism

NCT07800988 | Not Yet Recruiting

• 2 other identifiers: IRB-300016863SRA00001002
• Study Type: interventional
• Target: 20
• Locations: 0 countries
• Sites: N/A

Brief Summary

Obesity is associated with reduced metabolic flexibility (MetFlex), the capacity to shift between carbohydrate and lipid oxidation in response to nutrient availability. Grape polyphenols (resveratrol, catechins, quercetin, epicatechin) enhance fat oxidation and mitochondrial function in laboratory and animal studies, but whole grapes, rather than purified extracts, have not been tested for acute effects on MetFlex measured directly by whole-room calorimetry paired with mitochondrial function. This study integrates whole-room indirect calorimetry with high-resolution respirometry in peripheral blood mononuclear cells (PBMCs) to determine whether whole grape polyphenols shift the postprandial respiratory exchange ratio (RER) response to a high-fat meal and alter mitochondrial respiration, and whether responses differ by adiposity phenotype (lean vs. overweight/obesity).

Conditions

Obesity & Overweight; Healthy Adult

Keywords

Nutrition; Grapes; Energy balance; metabolic flexibility

Outcome Measures

Primary Outcomes (1)

• Postprandial Respiratory Exchange Ratio (RER)

  Response to High-Fat Test Meal (ΔRER), compared between grape powder and placebo conditions

  Measured continuously by whole-room indirect calorimetry from the high-fat test meal (~18:30) through the postprandial blood draw (~21:30), Day 1 of each 40-hour calorimeter stay.

Secondary Outcomes (4)

• Sleeping RER

  Overnight (~22:00-06:00; approximately 8 hours) Day 1 of each calorimeter stay

• Postprandial PBMC mitochondrial respiration

  Assessed from postprandial blood draw, 3 hours after test meal, Day 1 of each calorimeter stay

• DXA-derived Fat Mass

  Measured at screening

• Resting Energy Expenditure

  Measured at screening

Study Arms (2)

Grape Powder

ACTIVE COMPARATOR

Grape Powder Participants receive freeze-dried whole grape powder during a 40-hour calorimeter stay. Freeze-Dried Whole Grape Powder - 72 g, reconstituted with water, administered once per calorimeter stay, 30 minutes before the standardized high-fat test meal. Other name: whole California table grape powder.

Dietary Supplement: Freeze-Dried Whole Grape Powder

Placebo

PLACEBO COMPARATOR

Participants receive matched placebo during a 40-hour calorimeter stay. Placebo Powder - 72 g matched placebo formulated to replicate the sugar, fiber, organic acid, and sensory characteristics of the grape powder without polyphenolic compounds; administered on the same schedule.

Other: Placebo

Interventions

Freeze-Dried Whole Grape Powder DIETARY_SUPPLEMENT

72 g, reconstituted with water, administered once per calorimeter stay, 30 minutes before the standardized high-fat test meal. Other name: whole California table grape powder.

Grape Powder

Placebo OTHER

Placebo Powder - 72 g matched placebo formulated to replicate the sugar, fiber, organic acid, and sensory characteristics of the grape powder without polyphenolic compounds; administered on the same schedule.

Placebo

Eligibility Criteria

• Age: 25 Years - 60 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• Men and women aged 25-60 years
• BMI 18-24.9 kg/m² (lean phenotype, n=10) or BMI 25-40 kg/m² (overweight/obesity phenotype, n=10)
• Low habitual grape consumption
• Weight stable (no change \>5% in prior 6 months) and not actively attempting weight change
• White blood cell count within normal limits

You may not qualify if:

• Current smoking; drug or alcohol abuse
• Claustrophobia or psychiatric conditions that would make a 40-hour confined stay especially distressing or harmful
• Weight instability, recent/active weight-loss attempts, or structured exercise initiation during the study
• Hormone replacement therapy or medications known to affect metabolism
• Pregnant or breastfeeding
• Current or prior bulimia nervosa, binge eating disorder, or anorexia nervosa
• Grape allergy, or food allergies/intolerances precluding use of the metabolic kitchen
• Any condition that, in the PI's opinion, would make participation unsafe or could interfere with conduct/interpretation of the study

Sponsors & Collaborators

• University of Alabama at Birmingham: lead
• California Table Grapes Commission: collaborator

MeSH Terms

Conditions

Obesity; Overweight

Condition Hierarchy (Ancestors)

Overnutrition; Nutrition Disorders; Nutritional and Metabolic Diseases; Body Weight; Signs and Symptoms; Pathological Conditions, Signs and Symptoms

Study Officials

• Kathryn Whyte, PhD RDN

  University of Alabama at Birningham

  PRINCIPAL INVESTIGATOR

Central Study Contacts

Kathryn J Whyte, PhD RDN

CONTACT

2059754022; kjwhyte@uab.edu

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: QUADRUPLE
• Who Masked: PARTICIPANT, CARE PROVIDER, INVESTIGATOR, OUTCOMES ASSESSOR
• Masking Details: Randomization and dose preparation are performed by the metabolic kitchen, which maintains allocation concealment. Participants, investigators, and all other study staff (including the interventionist) remain blinded throughout.
• Purpose: PREVENTION
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Assistant Professor

Model Details: Two-period, two-treatment (grape powder vs. matched placebo) crossover; participants randomized to grape-first (AB) or placebo-first (BA) sequence, separated by a washout period.

Study Record Dates

• First Submitted: August 18, 2026
• First Posted: September 2, 2026
• Study Start: September 1, 2026
• Primary Completion (Estimated): July 1, 2027
• Study Completion (Estimated): September 1, 2027
• Last Updated: September 2, 2026

Record last verified: 2026-08

Data Sharing

• IPD Sharing: Will share
• Shared Documents: STUDY PROTOCOL
• Time Frame: 2028-2032
• Access Criteria: External investigators will need to create a data use agreement along with their IRB between institutions. Internal investigators will need to submit an internal IRB for any secondary analyses.