It is well established that any change in adiposity can greatly alter whole-body insulin sensitivity (12). In the current study, body weight was kept constant throughout the study, so that it would not be a confounding factor that contributed to the improved insulin sensitivity. Furthermore, participants were instructed not to alter their physical activity during the study. Even after controlling for certain variables, as expected for human studies, there was variability in insulin sensitivity values for both treatment groups. However, compared with the placebo group overall, insulin sensitivity improved significantly more in the blueberry group without any changes in body weight, adiposity, or energy intake. Also, no changes in body composition were observed in diet-induced obese mice fed whole blueberries (3). Another study (11) found the opposite in that whole blueberry supplementation increased body weight and adiposity in mice that were fed a high-fat diet with added blueberries compared with mice fed only a high-fat diet. The increase in the body weight and adiposity of the mice throughout the study could have potentially affected the outcome of unobserved improvements in glucose tolerance with whole blueberry supplementation, as discussed previously.