Defy your genetics; nature designed you to hold as little muscle and as much fat as possible. But fail no more. Our plan turns back your evolutionary clock—starting today

Men's Fitness, April, 2005 by Lou Schuler, John Williams

But all that brainpower is more high-maintenance than an Oscar-winning actress. While our brains provide just 2% of our body weight, they consume 20% of the calories we use every day, on average.

By comparison, a chimpanzee's brain uses 9% of its body's total energy, while an elephant's brain uses just 3%.

Maintaining that constant energy supply to the brain was a hell of a trick for our ancestors. Even though they ate everything--fish, meat, plants--they still had to adapt to moments when the menu featured "none of the above" That's another reason our lack of muscle is an advantage: We have slower metabolisms, which conserve fuel for our brains. Meanwhile, our bounteous fat cells allow us to store excess energy for lean times. Perhaps that's why we have about 10 times as many fat cells as other animals our size. No other primates--including gorillas--can store fat the way we can.

And while we can make our fat cells smaller, we can't make them go away. That's why it helps to remember that all those fat cells serve a purpose: to keep that big, energy-sucking brain of ours going, in good times and in bad.

FROM CAVEMAN TO COUCHMAN:

How to overcome your genetic limitations

Our hungry-brained, small-muscled, fat-storing ancestors got us to the top of the food chain without getting fat--and that's because cars, escalators, and remote controls had yet to be invented. A Columbia University study published earlier this year estimates that you would have to walk 5.7 hours a day over fields and hills to approximate the energy expenditure of early humans. If you're pressed for time, you could swim 3.7 hours a day or run more than 30 miles in about 3.4 hours.

In our era--hell, in our generation--we've managed to create so much separation between effort and result that we don't even have to hold up magazines with one hand while we masturbate anymore. We can just stare at a computer screen. The traditional advice is "eat less, exercise more" but if that worked, there'd be no obesity epidemic. Many of us simply can't exercise enough to get as lean as we want to be--we run out of time, energy, motivation, or knee cartilage. And a blanket admonition to "eat less" ignores the fact that none of us has the willpower to resist the excess food we face every day. Our bodies haven't forgotten that food means survival.

To overcome your genetics, "you have to do things that are counterintuitive,' says Steven Heymsfield, M.D., a weight-loss researcher at Columbia University. That's why the following advice revolves around one theme: getting the most out of the exercise you're able to do and the food you eat. The irony here is you're trying to get back to your caveman roots by doing exactly the opposite of what your ancestors would have done.

ANCIENT EATINGS

Here's the food your body was meant to have

Scientists don't like ii when people talk about specific diets being more in tune with what our prehistoric ancestors ate. "Their version of the South Beach Diet was to eat whatever didn't eat them first," says Erik Trinkaus, Ph.D., of Washington University. Still, there are lessons to be learned from the cavemen in our family tree, for whom "survival of the fittest" wasn't just a corporate slogan.