'Don't eat pasta,' 'Avoid any meats,' 'Eat only water, honey, and cayenne pepper' -- though nutrition activists offer no lack of weight-loss advice, when it comes to consistency they come up short. In a classic case of "quantity versus quality," food cop dictums are plentiful, but not generally useful in the long-term.  In contrast, the September issue of Scientific American boils down weight loss into one concise recommendation: physical activity.

The National Weight Control Registry collects the success stories of people who have lost at least 30 pounds and kept it off for a minimum of one year. The average individual in the group has maintained a weightloss of 70 pounds for over six years -- a sharp contrast to the average American dieter who ends up regaining any weight lost and then some. James Hill, a psychologist who helps run the registry, divulged to Scientific American the secret to successful weight loss:

"If you look at how they lost weight, there's no commonality at all" ... But "if you look at how they kept it off, there's a lot of commonality." The key, he continues, is exercise. "Activity becomes the driver; food restriction doesn't do it. The idea that for the rest of your life you're going to be hungry all the time-that's just silly."