|The Modern-Day Desk Sentence
"Our bodies have evolved over millions of years to do one thing: move," says James Levine,M.D., Ph.D., of the Mayo Clinic in Rochester, Minnesota, and author of Move a Little, Lose a Lot. "As human beings, we evolved to stand upright. For thousands of generations, our environment demanded nearly constant physical activity."
But thanks to technological advances, the Internet, and an increasingly longer work week, that environment has disappeared. "Electronic living has all but sapped every flicker of activity from our daily lives," Levine says. You can shop, pay bills, make a living, and with Twitter and Facebook, even catch up with friends without so much as standing up. And the consequences of all that easy living are profound.
When you sit for an extended period of time, your body starts to shut down at the metabolic level, says Marc Hamilton, Ph.D., associate professor of biomedical sciences at the University of Missouri. When muscles—especially the big ones meant for movement, like those in your legs—are immobile, your circulation slows and you burn fewer calories. Key flab-burning enzymes responsible for breaking down triglycerides (a type of fat) simply start switching off. Sit for a full day and those fat burners plummet by 50 percent, Levine says.
That's not all. The less you move, the less blood sugar your body uses; research shows that for every two hours spent on your backside per day, your chance of contracting diabetes goes up by 7 percent. Your risk for heart disease goes up, too, because enzymes that keep blood fats in check are inactive. You're also more prone to depression: With less blood flow, fewer feel-good hormones are circulating to your brain.
Sitting too much is also hell on your posture and spine health, says Douglas Lentz, a certified strength and conditioning specialist and the director of fitness and wellness for Summit Health in Chambersburg, Pennsylvania. "When you sit all day, your hip flexors and hamstrings shorten and tighten, while the muscles that support your spine become weak and stiff," he says. It's no wonder that the incidence of chronic lower-back pain among women has increased threefold since the early 1990s.
And even if you exercise, you're not immune. Consider this: We've become so sedentary that 30 minutes a day at the gym may not do enough to counteract the detrimental effects of eight, nine, or 10 hours of sitting, says Genevieve Healy, Ph.D., a research fellow at the Cancer Prevention Research Centre of the University of Queensland in Australia. That's one big reason so many women still struggle with weight, blood sugar, and cholesterol woes despite keeping consistent workout routines.
In a recent study, Healy and her colleagues found that regardless of how much moderate to vigorous exercise participants did, those who took more breaks from sitting throughout the day had slimmer waists, lower BMIs (body mass indexes), and healthier blood fat and blood sugar levels than those who sat the most. In an extensive study of 17,000 people, Canadian researchers drew an even more succinct conclusion: The longer you spend sitting each day, the more likely you are to die an early death—no matter how fit you are.