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It's not just the old and the obese who get diabetes. If you're young and lean, and you think flicking a TV remote or a video game controller is exercise enough, think again. You, too, can get diabetes in middle age.
New research on young adults in Minneapolis and three other cities found that being fit in early adulthood, regardless of weight, significantly decreases the chances of developing diabetes. But the slim and idle face a higher risk of the disease, defying its commonly held image.
For those who made fitness a New Year's resolution, the research offers an additional impetus to keep at it: Even if you are still overweight, the exercise could keep you free of this potentially deadly and incurable disease.
This study focused on the health effects of exercise in young adults. It concluded that those aged 18 to 30 with low or moderate fitness levels are six times likelier to develop diabetes than those who are highly fit. Fitness was measured on a treadmill.
"The big finding here is that [young adults] are already at substantial risk," said David Jacobs, a University of Minnesota epidemiology professor and co-author of a 15-year study of 4,500 people, including 1,400 in Minneapolis. The study "brings the point home in a very significant way," he said.
Researchers followed residents of Minneapolis, Chicago, Birmingham, Ala., and Oakland, Calif., who were 18 to 30 when the study began in 1985. As participants got older, researchers tested them for Type 2 diabetes, which typically occurs in adults. In this type of diabetes, the body develops a resistance to insulin, which is not able to keep blood glucose (sugar) levels in check.
Obesity long has been identified as a major risk factor for Type 2 diabetes, but researchers found that inadequate exercise in average-weight people placed them at higher risk. The study, which will conclude next year, was published in the Journal of the American Medical Association in December.
It underscores how fitness prevents diabetes. When you exercise, the body converts stored glucose into energy. Insulin helps the body transport glucose.
High blood-glucose levels -- a hallmark of Type 2 diabetes -- can damage proteins and other blood components, keeping them from working normally. That can lead to cataracts, kidney failure and heart disease.
"Insulin sort of acts as the key to the door for glucose to enter the muscle," said Don Dengel, a professor of kinesiology at the University of Minnesota. He was not involved in the study.
With continued exercise, the body becomes more adept at using insulin to take glucose from the bloodstream and putting it into muscles; but in some people who are physically inactive, the body can develop a resistance to insulin that potentially can become Type 2 diabetes, Dengel said.
"The message is that if you're 25 and you're unfit, you should probably do something about it," Jacobs said. "Diabetes is a very unpleasant disease, and people are getting it at younger and younger ages. It's partly due to the obesity that we're seeing in the U.S., but fitness is an independent component of it."
In Jacobs' view, the best reason to be fit at a young age is that "you can chase your grandchildren when you're older." But the pattern needs to be set early in life. His advice: "Establish a lifestyle and stick with it."
Obesity increasingly has became a public health concern as the numbers of overweight and obese people has soared.
Among many young people, the messages about keeping weight down and exercising haven't caught on.
"A lot of people believe that they're kind of invincible at age 25," Jacobs said. "It's very similar to cigarette smoking where young people say, 'I'm just doing this. I can quit any moment,' and they really can't. The same thing goes for people in their young adult years who are overweight and/or unfit."
By being unfit, he said, they're exposing themselves "to very significant disease" later in life.
The Centers for Disease Control and Prevention (CDC) calls diabetes "disabling, deadly and on the rise." Diabetes is a serious disease in itself, and caring for diabetic patients is expensive. It accounted for 11 percent of U.S. health care spending in 2002.
Diabetes can cause other serious problems, including heart disease, stroke, blindness, kidney failure, pregnancy complications, amputations of the toe, foot and leg, and deaths related to flu and pneumonia. The greatest risk is to the 5.9 million Americans who do not know they have the disease, the agency says.
That's one reason that state and federal health officials are trying to get out more information about diabetes. The other is to persuade people to exercise and maintain a healthy weight so they won't get the disease.
The federally funded study also linked a lack of fitness to high blood pressure and "metabolic syndrome," which is a mix of risk factors for diabetes and heart disease.
People who are overweight benefit from exercise even if the pounds stay on. "Even though you're still [overweight], there's still some advantage, according to this study, from being more fit," said Jacobs.
Other research supports that finding. A 15-year Texas study of 2,200 male diabetics found that those who were fit, regardless of whether they were obese or of normal weight, were less likely to die of any cause than those who were not fit.
The study's chief author, Dr. Timothy Church, medical director of the Cooper Institute in Dallas, called the study "a testament to the power of being physically active." The findings were published recently in the journal Diabetes Care.
It's increasingly clear that getting fit doesn't require marathon running, strenuous aerobic exercise or a huge time commitment.
It requires "getting out and raising your heart rate," and it could be done in 20 to 30 minutes of exercise three or four times a week, said Carrie Peterson, assistant clinical specialist in the University of Minnesota's Department of Food Science and Nutrition.
"Getting your heart pumping for 20 minutes to a half hour is going to increase your muscle mass, it's going to tone your body, it does wonders for your blood profile and you'll burn calories," she said.
Being lean isn't enough, she added.
Donna Halvorsen is at firstname.lastname@example.org.
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