Scientists are zeroing in on the culprit behind the over-hyped “epidemic” of obesity, and it’s not fast-food. Shocked? Don’t be — the answer is as near as your treadmill.

A team from Harvard studied a whopping 50,000 women for six years and determined that sedentary behavior is to blame for at least a third of all obesity, and 40 percent of diabetes cases. The researchers also focused on television-watching habits as an indicator of how little exercise many Americans are getting.

And the Centers for Disease Control and Prevention is now saying that the way neighborhoods are designed has a lot to do with it as well. The prevailing logic suggests that a cul-de-sac promotes less walking than traditional city blocks. “Obesity is not just [that] we’re eating more,” says the CDC’s Tom Schmid. “We’re getting less activity. People just don’t walk that much.”

These are just the latest hints that “Big Food” may not be the monster that activist groups like the Center for Science in the Public Interest make it out to be. Last fall, a National Bureau of Economic Research study concluded that fully 60 percent of our national weight gain can be traced back to an increasingly sedentary lifestyle. A recent University of Chicago study claims that obesity is the result of technological change and economic growth.

Syndicated columnist Bruce Bartlett noted in yesterday’s Washington Times that “societal pressures to stop smoking” have contributed to obesity. “Unfortunately,” he writes, “as most ex-smokers can attest to, purging nicotine from their systems” changed their body chemistry “so as to increase their weight.”

Even though an army of public health “experts” and nutritionists continue to home in on restaurants and food producers as uniquely blameworthy, an occasional honest broker escapes from the herd. Witness University of North Carolina researcher Lisa Sutherland, who concluded last week that lack of physical activity, not excessive caloric intake, is responsible for the growing rate of adolescent obesity. In a recent letter to The Washington Post, Sutherland wrote:

For two decades there has been an exponential increase in low-fat foods on the market, yet our society continues to be overweight. I highly doubt that an occasional large order of fries and a Big Mac are the main cause of obesity.

Will these messages make it into prime-time news coverage before the “obesity epidemic” hysteria washes over our lawsuit-happy culture like a tidal wave? Fat chance.