Grape Polyphenols and Second-meal Effect

Twenty‐five subjects with obesity will be were recruited. Detailed inclusion and exclusion criteria are provided below. The subjects will receive, after overnight fasting, either a monodose of freeze‐dried grapes (equivalent to 300 g of fresh grapes) or isocaloric placebo solved in water, together with a high‐fat breakfast. Blood samples will be collected before the intake, up to 5 h after breakfast, then a medium‐fat lunch will be provided and blood samples will be collected for three additional hours. Both interventions will be separated by two weeks. The following determinations will be performed in blood samples collected at different periods: glucose, insulin, triglycerides, uric acid, viscosity, antioxidant capacity. Additionally, a satiety test will be provided. It is expected that grape supplementation, as compared with an isocaloric placebo, causes significant modifications in all the parameters indicated. Nevertheless, the primary outcome of this study is the area under the curve for glucose after the second meal (300‐420 min from basal time).