Objective: Concord grape juice (CGJ) is a rich source of phenolic antioxidants, with a range of putative health benefits. However, high beverage energy and fructose intake may lead to weight gain and insulin resistance, respectively. This study assessed the effects of CGJ consumption for 12 weeks on appetite, diet, body weight, lipid profile, and antioxidant status.
Methods: Seventy-six men and women aged 18 to 50 years with a body mass index of 25.0 to 29.9 kg/m(2) consumed either 480 mL CGJ, 480 mL substitute (polyphenol-free) grape-flavored drink (SGD), or no beverage (NTG) daily for 12 weeks. Anthropometric indices were measured biweekly, dietary intake and appetite were assessed 4 times during the study, and plasma oxygen radical absorbance capacity, lipids, and oral glucose tolerance were assessed at baseline and week 12.
Results: Compared to baseline, the SGD group reported a reduction in fullness (p < 0.005) and gained 1.6 kg (p < 0.05). No significant changes in body weight or composition were observed with CGJ or control (no beverage added to diet). Mean dietary compensation was 98.8% for SGD and 81.0% for CGJ. Serum glucose and insulin area under the curve (180 minutes) increased slightly, but this was significant only with CGJ. Plasma antioxidant capacity did not differ across groups, suggesting no effect of chronic CGJ ingestion on antioxidant status.
Conclusions: Daily consumption of CGJ for 12 weeks did not lead to significant weight gain, but consumption of SGD did. The basis of this differential response could not be documented, but it is hypothesized to be a result of dietary compensation and effects of CGJ polyphenols on thermogenesis and substrate oxidation.