Getting regular, moderate-intensity exercise may be critically important for postmenopausal women who want to reduce their risk of cancer, heart disease and other chronic diseases, according to a study led by researchers at Fred Hutchinson Cancer Research Center in Seattle.The reason: exercise effectively reduces intra-abdominal fat, a hidden risk factor for many chronic illnesses including cancer, heart disease, and diabetes.

Lead investigator Anne McTiernan, M.D., Ph.D., a member of Fred Hutchinson's Public Health Sciences Division, and colleagues report the results of the largest randomized clinical trial to assess the effect of exercise on overall and intra-abdominal obesity in postmenopausal women in the Jan. 15 issue of the Journal of the American Medical Association. Researchers from Fred Hutchinson, the University of Washington, Yale University and the University of Colorado collaborated on the study.

"Even if a woman who exercises regularly doesn't see the benefits of dramatic weight loss on her scale, our results indicate that she can feel confident that she is improving her health, because regardless of the amount of weight lost, we now know that exercise reduces hidden intra-abdominal fat, the most dangerous type of fat," said McTiernan, director of Fred Hutchinson's Prevention Center. "This study gives us direct evidence that exercise can affect biology related to cancer and other chronic diseases in older women."

Reducing intra-abdominal, or visceral, fat is important because in addition to increasing the risk of cardiovascular disease and diabetes, among other conditions, such fat can raise insulin levels, which promotes the growth of cancer cells.  People with high levels of intra-abdominal fat may not even know it, McTiernan said, because it is hidden, deposited around the internal organs within the abdomen. "Most women don't know about intra-abdominal fat, but they should, since it is the most clinically significant type of fat and it's where women tend to store fat after menopause."

Although it is known that so-called "apple-shaped" people who store their fat around the stomach are at higher risk for conditions such as diabetes, hypertension and stroke than "pear-shaped" people who store their fat in their buttocks and thighs, visceral obesity is not necessarily correlated with body shape, McTiernan said. The only accurate way to determine the presence and extent of intra-abdominal fat is with imaging procedures such as CT or MRI scans. "Because it is so costly to measure intra-abdominal obesity, until now very little data has existed on the impact of exercise on this dangerous, hidden health risk," she said.

This yearlong study involved more than 170 previously sedentary, overweight, postmenopausal Seattle-area women. None took hormone-replacement therapy. Half were randomly assigned to a moderate-intensity, aerobic-exercise group and half, who served as a comparison group, attended a weekly hour-long stretching class.

The members of the exercise group, who worked out at home and at a gym for at least 45 minutes five days a week — an amount similar to current national recommendations — achieved significant reductions in weight, total body fat and intra-abdominal fat. After a year on the program, while the amount of body weight lost was modest yet statistically significant, the exercisers lost between 3.4 percent and 6.9 percent intra-abdominal fat while maintaining their calorie intake. Women who had the highest adherence to the program experienced the largest decreases in weight, total and intra-abdominal fat. The women in the stretching group, in contrast, experienced a slight gain in intra-abdominal fat.

"The beauty of exercise as a method to reduce total and intra-abdominal fat — and therefore chronic disease — is that it can be done by most women at low cost and with low risk of side effects. In addition, exercise has many other health benefits. The good news is that it is never too late to enjoy the health benefits of exercise," McTiernan said.

Another strength of this study was its randomized, controlled, clinical-trial design, considered the gold standard of study designs in medicine. The participants met three times a week with an exercise physiologist at an exercise facility, where they performed treadmill walking and stationary biking. They also exercised two days a week at home, doing exercises of their own choosing, mostly walking.

"In this type of study, we can directly control for extraneous factors and we directly observe what the women are doing rather than just relying on what they report on questionnaires. Therefore, we have more confidence in the results," she said.

"Most American women gain one to two pounds on average every year, and that adds up to dangerous levels over a lifetime. All women — especially those at risk for diabetes, cardiovascular disease, cancer or high cholesterol — need to stop gaining weight," she said. "Regular, moderate-intensity exercise can help keep the weight from creeping on, which can translate to improved health in the long run."

Women particularly benefitted from high activity over 20 years, gaining an average of 13 pounds less than those with low activity; while men with high activity gained about 6 pounds less than their low-activity peers. High activity included recreational exercise such as basketball, running, brisk walking or an exercise class or daily activities such as housework or construction work.

“Everyone benefits from high activity, but I was surprised by the gender differences,” said lead author Arlene Hankinson, M.D., an instructor in preventive medicine at Northwestern University Feinberg School of Medicine. “It wasn’t that activity didn’t have an effect in men, but the effect was greater in women. Now women should be especially motivated.”

The study will be published Dec. 14 in the Journal of the American Medical Association.

There could be several reasons for the gender difference, Hankinson said. Women are less likely than men to overestimate their activity, according to previous studies. “Men may not be getting as much activity as they report,” Hankinson explained.  In addition, men in the high-activity group compensated by eating more than their low-activity counterparts, which could have led to more weight gain. The highly active women didn’t eat more than low-activity women in the study.

There were many ways to achieve the study’s definition of high-activity levels, Hankinson noted. One way was 150 minutes of moderate to vigorous activity a week.

The study participants -- 1,800 women and nearly 1,700 men — are part of the Coronary Artery Risk Development in Young Adults (CARDIA) Study, a multi-center, longitudinal and population-based observational study designed to describe the development of risk factors for coronary heart disease in young black and white adults.

Coauthor Stephen Sidney, M.D., associate director for clinical research at the Kaiser Permanente Division of Research. “Common medical problems such as heart disease, diabetes and obesity have their origins in childhood and can generally be prevented by maintaining a normal weight, not smoking, exercising regularly and eating a healthy diet throughout life.”

Hankinson’s research is the first to measure the impact of high activity over 20 years between young adulthood and middle age and to frequently examine participants (seven times) over that period. Study participants are more likely to remember and accurately report their behavior with regular exams, she said.   Previous studies, Hankinson said, looked at a single exercise intervention’s effect on weight for a short period of time or examined participants in longer studies at only two points in time -– the beginning and the end.

“We wanted to see if people’s activity levels during their youth were enough to help them keep weight off in middle age, or if they needed to up the ante,” Hankinson said. “It’s difficult to avoid gaining weight as you age. Our metabolic rate goes down. We develop conditions or have lifestyles that make it harder to maintain a high level of activity.”

“The study reinforces that everyone needs to make regular activity part of their lifestyles throughout their lives,” she said. “Not many people actually do that.” The active group in the study comprised only 12 percent of the participants.  Lower levels of activity had a negligible effect on weight gain in the study. “High activity was the only kind that made a significant difference,” Hankinson noted.

The study is the first to examine the effect of aerobic exercise on middle-aged and older adults with a diagnosis of insomnia. About 50 percent of people in these age groups complain of chronic insomnia symptoms.  The aerobic exercise trial resulted in the most dramatic improvement in patients’ reported quality of sleep, including sleep duration, compared to any other non-pharmacological intervention.

“This is relevant to a huge portion of the population,” said Phyllis Zee, M.D., director of the Sleep Disorders Center at Northwestern Medicine and senior author of a paper to be published in the October issue of Sleep Medicine. The lead author is Kathryn Reid, research assistant professor at Feinberg.

“Insomnia increases with age,” Zee said. “Around middle age, sleep begins to change dramatically. It is essential that we identify behavioral ways to improve sleep. Now we have promising results showing aerobic exercise is a simple strategy to help people sleep better and feel more vigorous.”   The drug-free strategy also is desirable, because it eliminates the potential of a sleeping medication interacting with other drugs a person may be taking, Reid said.

Sleep is an essential part of a healthy lifestyle, like nutrition and exercise, noted Zee, a professor of neurology, neurobiology, and physiology at Northwestern University Feinberg School of Medicine and a physician at Northwestern Memorial Hospital.

“Sleep is a barometer of health, like someone’s temperature. It should be the fifth vital sign. If a person says he or she isn’t sleeping well, we know they are more likely to be in poor health with problems managing their hypertension or diabetes," notes Zee.

The study included 23 sedentary adults, primarily women, 55 and older who had difficulty falling sleep and/or staying asleep and impaired daytime functioning. Women have the highest prevalence of insomnia. After a conditioning period, the aerobic physical activity group exercised for two 20-minute sessions four times per week or one 30-to-40-minute session four times per week, both for 16 weeks. Participants worked at 75 percent of their maximum heart rate on at least two activities including walking or using a stationary bicycle or treadmill.

Participants in the non-physical activity group participated in recreational or educational activities, such as a cooking class or a museum lecture, which met for about 45 minutes three to five times per week for 16 weeks. Both groups received education about good sleep hygiene, which includes sleeping in a cool, dark and quiet room, going to bed the same time every night and not staying in bed too long, if you can’t fall asleep.

Exercise improved the participants’ self-reported sleep quality, elevating them from a diagnosis of poor sleeper to good sleeper. They also reported fewer depressive symptoms, more vitality and less daytime sleepiness. “Better sleep gave them pep, that magical ingredient that makes you want to get up and get out into the world to do things,” Reid said.

The participants’ scores on the Pittsburgh Sleep Quality Index dropped an average of 4.8 points. (A higher score indicates worse sleep.) In a prior study using t’ai chi as a sleep intervention, for example, participants’ average scores dropped 1.8 points.

“Exercise is good for metabolism, weight management and cardiovascular health and now it’s good for sleep,” Zee said.

The research was funded by the National Institute on Aging.