For nine years, 47-year-old Detroiter Elizabeth Schneider has exercised for 40 minutes, three times a week. Her workouts have held her weight at a steady 145 pounds, which is in the ideal range for her 5-foot-9 frame.
While studies show most American women her age are overweight, Schneider is fit. But one new report suggests she might not be for long.
Schneider's workouts aren't likely to be enough to maintain her weight as she ages, according to findings reported late last month in the Journal of the American Medical Association.
The report built on research conducted at Harvard's Brigham and Women's Hospital, which followed 34,079 nondieting, middle-age women for 13 years, and found that women with a body mass index less than 25 needed 60 minutes of daily moderate activity to ward off weight gain.
"It seems like that is asking a lot," Schneider said before a floor aerobics class at the South Oakland Family YMCA in Royal Oak, Mich.
She says she doesn't diet, but looking after her 15-year-old son and 13-year-old daughter helps keep her active.
"I eat dessert," Schneider says, "pretty much every day."
Since 2008, the U.S. Centers for Disease Control and Prevention has recommended adults get 150 minutes — 30 minutes, five days a week—of moderate activity. The CDC also recommends twice weekly strength-training sessions.
Dr. Caroline Richardson, an associate professor of family medicine at the University of Michigan, says that even though the study suggests more activity is needed, the recommendation has not changed. "We should be doing 150 minutes a week, that's a given," says Richardson, who reviewed the study's findings. "There is nothing in this report that says we shouldn't be doing that. "
Richardson says she knows the 150-minute weekly mandate is already hard for many busy women to meet. She hopes the new study won't scare people into doing nothing because it sounds like too tall a challenge.
"I think the data is interesting and the study well-done," Richardson said. "But it has some built-in weaknesses."
It was an observational study, and observational studies are inherently less conclusive than controlled studies, Richardson said.
The women also self-reported their exercise, and that method has known pitfalls, too, as people both over- and underreport their actions. The final issue is that the researchers collected information on the women's diets only at the beginning of the 13-year project.
The baseline diet was also self-reported, which Richardson said is "very weak," as people tend to underreport their eating habits.
"We don't exactly know what happened here," Richardson said. But from previous research, "it's clear that diet is the driver for weight loss, not exercise."
The report also concluded that 30 minutes of daily intense activity such as running would keep women from gaining weight as they age.
Jane Walbridge, 49, of Royal Oak thinks the new research is right on. Walbridge does floor aerobics twice weekly and yoga four times a week. She also walks or rides her bike almost daily. She's been following that regime since 2000.
"I find my own weight is getting harder to keep down," Walbridge says. "In my 40s, I've started to notice I had to exercise more to stay the same size."
Sue Vian , 60, of Royal Oak disagrees. She says she's the same size she was in high school and hasn't increased her activity level much in the past decade. The retired first-grade teacher has taken a floor aerobics class twice a week for four years. She also walks and rides a stationary bike. She does all her own house cleaning, which can count as moderate exercise.
"I think an hour a day is a lot to ask people to do. People are busy. It's not realistic, and it's going to turn people off," Vian said.