In this week's news: Fast food may make grades sink fast; there's new evidence that resveratrol in red wine may carry ancient benefits; kids diet for the darnedest reasons (i.e., the best!).

Could feeding your kids fast food put them on the fast track to lower grades? A nationwide study published in the journal Clinical Pediatrics found that fifth graders who frequently consumed fast food had lower test-score gains in reading, math and science by eighth grade. The link held true even after the researchers controlled for other factors, including how much the kids exercised and watched TV, what other foods were in their diets, the socioeconomic status of their family, and what their school and neighborhood were like. Although the study did not determine causality, the authors suggest the link may have to do with a lack of nutrients, like iron, that boost cognitive development and with high amounts of fat and sugar, which may affect memory and learning, noting that the results "suggest [children's] fast-food consumption should be limited as much as possible."

Teens today — it looks like we can actually learn a thing or two from them, even when it comes to diet and weight loss. An in-depth study of teens who had been obese or overweight and then lost weight and kept it off found that they’d been motivated to shape up for their own good — to be healthier and to feel better — rather than to please their parents or peers. "Our findings suggest that teens have motivations that are more intrinsic," study author Chad Jensen, a psychologist at Brigham Young University, said. "One implication is that parents should help to focus their teen on healthy behaviors for the sake of being healthy more than for social acceptance." Support during major life transitions, an emphasis on healthy food options and a commitment to making slow, steady progress during long-term goals are also key, Jensen said.