Kathryn Schmitz is a realist. She knows that for many women the current federal exercise guidelines, which call for 30 to 60 minutes of physical activity at least five days a week, seem like a joke. A bad joke.
Schmitz, an assistant professor of epidemiology in the School of Medicine, is hardly a slouch. A former dancer, Schmitz has spent her academic career studying the connection between physical activity and disease.
As a busy mother of two boys under the age of 10, though, she can relate to women who find it challenging to fit exercise into their daily routine. That’s one of the reasons she decided to find out if doing just 30 minutes of weight training twice a week could have an effect on the slow, steady abdominal weight gain many women experience from their 20s through their 40s.
For her study, Schmitz divided in two a group of 164 overweight and obese women aged 24 to 44. One group was given a two-year membership at the YMCA and four months of supervised strength training classes. After the initial training period the women were instructed to continue twice weekly sessions on their own, with booster classes four times a year.
Women in the other group—the control group—were given brochures recommending 30 minutes to an hour of exercise most days of the week.
To determine the effect of the exercise on intra abdominal fat—the fat that wraps around the internal organs and is closely associated with heart disease and diabetes—Schmitz had CT scans taken of the women’s abdomens at the point in the back between the second and third lumbar vertebrae. Over the two years the women in the control group who had been encouraged to take daily exercise saw a 21 percent increase in intra abdominal fat. For the weight lifting group, the increase was only 7 percent.
“I was surprised by the magnitude of the results,” says Schmitz, who notes that by using accelerometers and motion detectors she was able to ascertain that the control group did not change its level of physical activity during the study period. In other words, the advice in the brochures fell on deaf ears. The strength trainers, by contrast, kept to their twice-a-week schedule faithfully.
Schmitz is quick to point out, “We’re not saying you shouldn’t be doing aerobic exercise.” In fact, studies have shown that aerobic exercise reduces intra-abdominal fat. “From the public health perspective, I’m interested in what’s really feasible,” she says, “and I know for myself, with two children and being an academic, twice a week going to the gym is something I can handle.”
The idea of the “tolerable dose” intrigues her, and she draws an analogy to the strategy adopted by drug companies. “When they test the efficacy of a drug, one of the things that’s important is if it’s tolerable at the recommended course of treatment. Is it something the patient will do? There was a time when antidepressants had to be taken multiple times a day. If you’re going to market something it has to be behaviorally feasible. We demand this of our drugs. If a drug is much better but you have to take it three times a day it won’t sell as much.”
The recommended 30 to 60 minutes of activity daily, she says, “is not a tolerable dose,” and because of that less than 25 percent of us are doing it.
Two weekly sessions at the gym may be more doable, but Schmitz concedes that when she explains her study to people she still finds it a tough sell in terms of a public health message. “I can just see the infomercial,” she says. “Follow this program and you can stay exactly where you are! Most people when you talk about weight control want the end result to be that they look like Halle Berry or Heather Locklear.” The truth is, she says, American women gain one to two pounds a year from their mid-20s on. “That’s a significant weight gain, and a significant risk,” says Schmitz, and to prevent that increase, even if you’re not actually losing weight, can make a big difference healthwise.
Schmitz says it’s about modifying your expectations to fit reality as you enter middle age. “My goal at this point is to weigh at 50 what I weighed at 40.”
Originally published on April 13, 2006