Exercise is a necessary means for fighting flab, but it also helps prevent diabetes even if you don't lose weight. During physical activity, muscle cells quickly burn up stored fuel. In need of more energy to keep working, they become less insulin-resistant and refuel by soaking up glucose, which lowers blood sugar levels. Any type of activity appears to have this effect, whether it's aerobic exercise or resistance training. "Doing both is probably better than either one alone," says Ronald Sigal, M.D., a specialist in diabetes research at the University of Ottawa, Canada.
Working out has an immediate effect on glucose levels, though the benefit fades within 24 hours or so. "Look at it as a drug you need to take regularly," says exercise physiologist Joseph A. Houmard, Ph.D., of East Carolina University in Greenville, N.C. But you needn't overdose. In a 2003 study, Houmard and his colleagues asked overweight subjects with insulin resistance to take brisk walks, totaling 170 minutes per week. A second group jogged for 115 minutes per week, but the walkers lowered their insulin resistance twice as much as the joggers.
That's good news for Susan Hicks, who now takes frequent three-mile walks with her beagle. She's given her diet a workout, too, by reducing her soda intake, drinking more tea, and eating salads with meals to curb her appetite. Since learning she has prediabetes, Hicks has kept her blood sugar in check, lost 10 pounds, and gained a sense of optimism and control. "Lately," she says, "I feel very positive."