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Strong People

Live Fat, Die Old?

What’s missing from the news on obesity and longevity

In November 2007, the Journal of the American Medical Association published a provocative study by Katherine Flegal and others that showed how body mass index (BMI), a measurement of obesity using height and weight, is related to specific causes of death. Unsurprisingly, the results indicated that people who are obese have a higher risk of dying from cardiovascular disease and breast, colon, esophageal, uterine, ovarian, kidney, and pancreatic cancers.

But the study also produced an unexpected result: it suggested that being overweight might actually lower your risk of dying from other causes, such as emphysema, Alzheimer’s disease, and pneumonia.

On the surface, this finding seems to weaken the case for maintaining a healthy weight and a healthy lifestyle. But we are just beginning to learn about the relationship between BMI and cause of death—we still have a long way to go before we understand it completely. In addition, we need to keep in mind that the research looked solely at death statistics. It did not give any information about the subjects’ quality of life or the condition of their health before death.

To me, those are the most important issues. The purpose of leading a healthy lifestyle isn’t simply to prolong your life. Rather, it is to prolong the years that you are able to lead a full, active life. And a lot of data shows that maintaining a healthy weight and a lifestyle full of physical activity and good nutrition does indeed ensure a high quality of life.

Consider the data on depression. More than 6 million Americans age 65 and older are depressed. The malady is so common among the elderly that some believe it is a normal part of aging. Yet research suggests otherwise: instead, people often become depressed because of physical health problems.

We have evidence that keeping up a regular program of physical activity can play a big role in staying depression-free. Some colleagues at Tufts examined the effects of a strength-training program on depression in older adults. Thirty-two subjects aged 60 or older who had been diagnosed with depression were randomly assigned to either an exercise group or a control group. The exercise group participated in strength-training two or three days a week for 20 weeks. The control group attended a series of health education lectures for 10 weeks, but did not exercise regularly. After 20 weeks, the people in the exercise group showed significantly reduced depression: 73 percent of the exercisers were classified as non-depressed, compared with only 36 percent of the non-excercisers.

Other research demonstrates that staying active can help forestall physical limitations—the musculoskeletal and joint problems that make it harder to engage in daily activities such as climbing stairs, doing housework, or walking. In a study that followed 356 men and women aged 65 to 95 for six years, researchers found that those who walked often for exercise were nearly twice as likely to age without developing physical limitations.

Another study followed more than 5,000 people aged 70 years and older who already had physical limitations. Those who did a minimal amount of physical activity—the equivalent of walking at least one mile, one day per week—were 55 percent less likely to develop severe physical limitations, problems such as extreme muscle weakness or joint pain that could rob them of their physical independence entirely.

So while we still have a lot to learn about the aging process, we need to recognize that we have some important knowledge already. Specifically, we know that keeping up a healthy lifestyle is one of the best things we can do to make sure we age gracefully.

MIRIAM E. NELSON directs the John Hancock Center for Physical Activity and Nutrition at Tufts. She is an associate professor at the Friedman School of Nutrition Science and Policy and an adjunct professor at the Tisch College of Citizenship and Public Service. She is author of the bestselling Strong Women book series (Putnam).

  © 2008 Tufts University Tufts Publications, 80 George St., Medford, MA 02155