"When we looked at those 14% -- these are fat ladies but physically active -- they had much lower blockages of their coronary arteries, much lower fasting blood sugars, they had narrower waists, and they had much lower triglycerides, and when we lump those together, that's a bit of the insulin-resistance syndrome," Merz tells WebMD. "These overweight ladies are at risk for insulin resistance and diabetes, but if you're physically active, then the overweight part doesn't turn into insulin resistance."
You don't have to be overweight to see real benefits from even modest exercise, agrees I-Min Lee, MBBS, ScD, associate epidemiologist at Brigham and Women's Hospital and associate professor of medicine at Harvard Medical School in Boston. Lee is the author of the JAMA article.
"Our study found that walking at least an hour a week regardless of pace is associated with lower risk of heart disease, and this is a lesser level of physical activity than has been shown in previous studies," Lee tells WebMD. She says that it's only human nature to try to get away with as little as possible, including exercise. And when recommendations change as they have over the past few years -- from "No pain, no gain" (go all-out at least three times per week) to "train, don't strain" (exercise less strenuously but more frequently), people tend to get confused.
Interestingly enough, both approaches burn off about the same amount of calories, Lee says. "It's just offering people a choice: Do you want to do it vigorously over a short period of time, or do you want to do it moderately over a longer period of time. We really don't have a lot of information, especially in women, regarding the kinds of intensive activities that might be beneficial for them."
Lee and colleagues looked at data on nearly 40,000 women who took part in a nationwide health study, and looked for a relationship between exercise and recreational activities and coronary heart disease. In all, there were 244 cases of coronary heart disease, and after the researchers eliminated other possible causes of heart disease, they found that women who walked at even a leisurely 2 to 3 miles per hour still had about a 44% to 30% lower risk for heart disease than women who never get moving at all.