Nutrition Action article - Inactivity- page 1

Planning to exercise more? Been planning on it for a while?

It's easy to put off, at least today, at least this week, at least until you (choose one) get new sneakers, get past the holidays, get some free time, get a new job, get the kids off to college, whatever.

But as the years slip by, your body isn't just frozen in time, waiting to get moving. It's fading.

"If muscle isn't stimulated, your body senses that you don't need it," explains Miriam Nelson of Tufts University in Boston. "Metabolically, it's expensive to keep up so you start to lose it."

Muscle is just the beginning, she adds. "Inactivity affects the brain, heart, blood vessels, bones, liver, gut, sleep, anxiety, depression, self-esteem, your ability to use glucose, and more."

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"From the top of your head to the bottom of your toes, being physically active is the stimulus that gets most organs in the body to work at their best," says Tufts University exercise expert Miriam Nelson.

"If you're not active, it affects all body systems, literally down to the cellular level, where your ability to transfer oxygen from the bloodstream to cells is diminished and the number of power-producing mitochondria in your cells is less."

"If you can't get as much oxygen out of your blood, you can't walk up a flight of stairs as easily as you get older." And that's just one system that suffers if you're sedentary.

The good news: it's never too late to start moving. "Well into your 90s, all of these systems can be stimulated," notes Nelson. "It's quite remarkable."

Here are 10 ways inactivity can take a toll on your body.

1 Diabetes

"The one thing that seems to deteriorate quickest with inactivity is insulin sensitivity," says Ben Hurley, a professor of kinesiology at the University of Maryland at College Park (and husband of Nutrition Action's Jayne Hurley). Fortunately, "it also responds most consistently when you train."

Type 2 diabetes--by far the most common kind--occurs when the body be comes insensitive, or resistant, to insulin in the blood. When insulin stops working, blood sugar levels rise and diabetes sets in.

Regular exercise reverses the damage.

"It increases insulin sensitivity and makes the cells better at taking in glucose and processing it," explains I-Min Lee, an associate professor of epidemiology at the Harvard School of Public Health in Boston.

In a study of more than 50,000 nurses, every two hours a day of TV-watching was linked to a 14 percent increase in the risk of diabetes. (1) Every two hours of sitting at work was linked to a 7 percent increase. In contrast, every hour of brisk walking per day was linked to a 34 percent lower risk.

What's more, when researchers told people with high-but-not-yet-diabetic blood sugar levels to do aerobic exercise for at least 2 1/2 hours a week and lose at least 7 percent of their body weight, their risk of diabetes was 58 percent lower than similar people who didn't exercise or lose weight. (2)

"The data are striking," says Hurley. And it's not just an issue for adults. "Type 2 diabetes used to be a disease of middle age," he adds. "But now we're seeing it in young people. It's a sedentary disease."

Hurley sounds like researcher Steven Blair talking about the metabolic syndrome, which raises the risk of both diabetes and heart disease. Doctors diagnose the syndrome when people have a large waist, low HDL ("good") cholesterol, and elevated (though not necessarily high) blood pressure, blood sugar, and triglycerides.

"The metabolic syndrome is misnamed," says Blair, who is president of the Cooper Institute in Dallas, Texas. "It ought to be called the inactivity syndrome."

2 Cancer

"The evidence is fairly clear now that men and women who are physically active have a 30 to 40 percent lower risk of colon cancer compared to individuals who are not active," says Harvard's I-Min Lee, who examined dozens of studies. (3)

Experts have several theories that might explain how physical activity protects the colon. "It increases transit in the intestine, which makes food flow through fast," says Lee. "So any carcinogens in the intestine have less contact with the cells that line the intestine."

Another possibility is that regular exercise shores up the immune system. "That would protect the body from any cancer, including colon," she adds,

Hormone-like substances called prosta glandins might also play a role. "Activity can decrease prostaglandin E2 levels in the intestinal cells," says Lee. "Prostaglandin E2 is associated with a higher risk of colon cancer," she notes, probably because it makes colon cells proliferate faster and slows intestinal motility.

Then there's the obvious: "Physical activity prevents weight gain, and the overweight have a higher risk of colon cancer," says Lee.

How much movement is enough? "We don't have precise data, but it looks like you need 30 to 60 minutes a day of moderate-intensity physical activity."

Regular exercise also appears to lower the risk of breast cancer by about 20 percent. (4) "But the research has been somewhat inconsistent," says Walter Willett, chair of the nutrition department at the Harvard School of Public Health.