May 3rd, 2010
In a 2005 article in Science magazine, James A. Levine, an obesity specialist at the Mayo Clinic, pinpointed why, despite similar diets, some people are fat and others aren't. "We found that people with obesity have a natural predisposition to be attracted to the chair, and that's true even after obese people lose weight," he says. "What fascinates me is that humans evolved over 1.5 million years entirely on the ability to walk and move. And literally 150 years ago, 90% of human endeavor was still agricultural. In a tiny speck of time we've become chair-sentenced," Levine says.
Hamilton, like many sitting researchers, doesn't own an office chair. "If you're standing around and puttering, you recruit specialized muscles designed for postural support that never tire," he says. "They're unique in that the nervous system recruits them for low-intensity activity and they're very rich in enzymes." One enzyme, lipoprotein lipase, grabs fat and cholesterol from the blood, burning the fat into energy while shifting the cholesterol from LDL (the bad kind) to HDL (the healthy kind). When you sit, the muscles are relaxed, and enzyme activity drops by 90% to 95%, leaving fat to camp out in the bloodstream. Within a couple hours of sitting, healthy cholesterol plummets by 20%.
The data back him up. Older people who move around have half the mortality rate of their peers. Frequent TV and Web surfers (sitters) have higher rates of hypertension, obesity, high blood triglycerides, low HDL cholesterol, and high blood sugar, regardless of weight. Lean people, on average, stand for two hours longer than their counterparts.
The chair you're sitting in now is likely contributing to the problem. "Short of sitting on a spike, you can't do much worse than a standard office chair," says Galen Cranz, a professor at the University of California at Berkeley. She explains that the spine wasn't meant to stay for long periods in a seated position. Generally speaking, the slight S shape of the spine serves us well. "If you think about a heavy weight on a C or S, which is going to collapse more easily? The C," she says. But when you sit, the lower lumbar curve collapses, turning the spine's natural S-shape into a C, hampering the abdominal and back musculature that support the body. The body is left to slouch, and the lateral and oblique muscles grow weak and unable to support it.
Via Marisa Anderson.