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Getting regular, moderate-intensity exercise may be critically important for men and women who want to reduce their risk of cancer, heart disease and other chronic diseases, according to a study led by the Public Health Sciences Division's Dr. Anne McTiernan. The reason: Exercise effectively reduces weight, overall body fat and intra-abdominal fat, a hidden risk factor for many chronic illnesses. The results of the largest randomized clinical trial to assess the effect of exercise on overall and intra-abdominal obesity, among other variables, in women and men appear in the June issue of Obesity. Researchers from the Hutchinson Center, University of Washington, VA Puget Sound Health System, Virginia Mason Medical Center, Yale University and University of Alberta collaborated on the study.
The results support and build upon findings of a previous study in postmenopausal women, reported by McTiernan and colleagues in 2003, which indicated regular exercise effectively reduced intra-abdominal fat.
"Even if those who exercise regularly don't see dramatic weight loss, our results indicate that people can feel confident that they are improving their health. The reason is because regardless of the amount of weight lost, we found that exercise reduces overall body fat and hidden intra-abdominal fat, the most dangerous type of fat," said McTiernan, director of Fred Hutchinson's Prevention Center and an international expert on the impact of physical activity on cancer prevention. "This study gives us direct evidence that exercise can affect biology related to cancer and other chronic diseases not only in women, but in men as well."
The amount of intra-abdominal fat lost was substantial; the female exercisers lost 5.5 percent and the male exercisers lost 7.5 percent after a year of regular exercise.
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 people don't know about intra-abdominal fat, but they should, since it is the most clinically significant type of fat. It is also where women tend to store fat after menopause and where men tend to store it at any age."
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 in both men and women," she said.
The study, which was funded by the National Cancer Institute and the National Institutes of Health, involved 202 healthy, sedentary Seattle-area men and women between the ages of 40 and 75. Half of the participants were randomly assigned to an exercise group and half were randomly assigned to a comparison, or control group. The exercisers were asked to engage in moderate to vigorous activity for an hour per day six days a week for a year, both on their own and at a one of several exercise facilities (including one located at the Hutchinson Center).
"This study really underscores the new activity recommendations from the USDA and the Institute of Medicine, both of which advise people to exercise an hour a day, six days a week for weight control and general health," McTiernan said.
The participants also were asked to maintain their regular eating habits for the duration of the study. Those in the control group were asked to maintain their current activity level and diet for a year, after which they had an opportunity to exercise for two months at no cost with a personal trainer at one of several study facilities. The Seattle Foundation and Precor Inc. of Bothell donated exercise equipment for the state-of-the-art Hutchinson Center exercise facility.
Adherence to the program was excellent, as indicated by daily exercise logs; 80 percent of the exercisers met more than 80 percent of their six-hour-a-week goal.
"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 people 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.
Strengths of this study — compared to previous trials that looked at the impact of activity on weight, body fat and intra-abdominal obesity — include the following:
- The large sample size (202 versus fewer than 25 subjects) and the length of the exercise intervention (one year compared to less than six months);
- high adherence rates (80 percent of the exercisers completed 80 percent or more of their prescribed 360 minutes per week of exercise); and
- its randomized, controlled, clinical-trial design, considered the gold standard of study designs in medicine.
"In this type of study, we can directly control for extraneous factors and we directly observe what the men and women are doing rather than just relying on what they report on questionnaires. Therefore, we have more confidence in the results," she said.
The results of the study are significant for men and women who seek a natural way to reduce their risk of chronic disease, said McTiernan, who is also a research professor at the University of Washington School of Medicine and School of Public Health and Community Medicine.
"Most Americans gain one to two pounds on average every year, and that adds up to dangerous levels over a lifetime. Men and 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."
Seattle-area women needed for NEW diet, exercise study
Center researchers seek more than 200 healthy, overweight and sedentary postmenopausal women who live in the Seattle area to participant in a study that examines the effects of exercise and nutrition on breast-cancer risk factors.
The National Cancer Institute-funded Nutrition and Exercise for Women (NEW) Study needs women ages 50 to 75 who are willing to travel to the Hutchinson Center for a yearlong exercise and/or nutrition intervention.
Eligibility requirements include being a nonsmoker, not using hormone therapy for the past six months, getting less than an hour of moderate activity per week, and being above a certain weight threshold, depending upon height.
Those who qualify must be willing to not participate in any other exercise or weight-loss programs during the 12-month study enrollment and must be willing to receive random assignment into one of four following groups:
- Moderate-intensity aerobic exercise for 45 minutes a day, five days per week for a year;
- a reduced-calorie diet for a year;
- aerobic exercise and a reduced-calorie diet for a year; or
- no intervention (to serve as a control, or comparison, group).
At the end of the yearlong study, women in the control group will receive a free, two-month pass to the Center's state-of-the-art exercise facility and get to work out under the supervision of a personal trainer. They'll also get a chance to attend four group weight-loss meetings and will receive a variety of educational handouts about diet and exercise.
The study will take place at Hutchinson Center's Prevention Studies Clinic. Designated parking for study participants is free.