Vitis Intervention Trial in Substrate Metabolism

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).