Zigzag dieting: if you can keep your body guessing and your appetite in check, you'll continue to lose lard. This special six-step calorie-cycling plan will do just that for you, sparing your muscle while burning your fat in just six weeks

If you've been on a diet before, you're all too aware of the standard outcome: You cut back on your food and you lose weight ... at least initially. But then your progress slows to a crawl, before stopping altogether. At this point, no matter how strict you are with your calories, no matter how much you work out, the pudge won't budge.

What gives? Your body's natural instinct to preserve itself at all costs kicks in. Sensing a calorie deficit, your body shifts into starvation mode, shutting down all fat burning as it hoards calorie stores.

Even if you're successful at losing a few pounds, your body often reacts by adjusting your energy expenditure in order to revert to your previous weight, known as your "setpoint." A 1995 study out of the Laboratory of Human Behavior and Metabolism at Rockefeller University in New York measured both obese and non-obese people who either increased or decreased their body weight 10 percent to 20 percent. In both cases, metabolism shifted--at a lower weight, the subjects began burning less energy throughout the day, while at a higher weight they burned more, an effort by their bodies to return to that setpoint.

These metabolic shifts, meant to preserve you in times of starvation, were great in prehistoric days, when men didn't know when or from where their next mastodon steak was coming and paid no mind to crafting a six-pack. But if you covet beach-worthy muscle, these annoying physiologic mechanisms will quash your efforts every time--unless you learn to make them work for you. That's where calorie cycling comes into play.

The following diet alterations are built to take advantage of the normal metabolic process: When your body wants to return to your setpoint, you jolt it with a surplus of calories. From there, you cycle your eating patterns, which will ignite the pilot light in your fat-burning furnace and help you forge a chiseled physique.

WHY CYCLE?

First off, a warning: Although bodybuilders, and others interested in a toned, muscular build, have successfully applied some form of calorie cycling to their diets for years, the approach does not have much research to back it up. Most studies on the subject of manipulating calorie intake center on obese individuals; none focuses on the use of calorie cycling to get lean. That said, scientific evidence which can be gleaned from the available research shows that altering calorie intake can lower fat while preserving muscle.

If you've dieted for a while now with no discernible fat loss, the plan we present is designed with the available research in mind and will blast you right off that plateau. It begins with a 10-day period of eating more calories than your body actually needs, a step designed to kick-start your metabolism into using fat for fuel.

From there, you'll go into a weeklong cycle of five days of eating 500 fewer calories than your body needs, followed by two days of eating above your maintenance calorie level. These five-days-low, two-days-high stints may not have any additional effects on your metabolism, but they will help you stay the dietary course, says Kristin Reimers, M.S., R.D., associate director of the International Center for Sports Nutrition in Omaha.

"The benefit of cycling rather small calorie swings over short periods of time probably helps more by making the diet easier to stick with, not so much by tricking the metabolism," Reimers says. "Short-term cycling can provide a dieter some cheat days without guilt, and quite frankly, that is very important. One mind-set that thwarts many weight-loss attempts is the black-and-white thinking that dieting is an all-or-none deal; if you go off for one day, you've blown it, it's over. The cycling provides higher-calorie days to overcome that mind-set, and can work for fat loss so long as a long-term calorie shortfall is achieved."

SMALL CHANGES FOR BIG RESULTS

Another piece of good news is that manipulating your calorie intake does not mean you'll have to keep detailed records--you'll merely log what you scarf down for the first few days--or meticulously measure out your foods. This six-step plan doesn't involve grand-scale changes to your current eating plan, but just some simple cleaning up, some additions and subtractions of foods depending on where you are in the cycle and a touch of discipline to eat every three hours instead of cramming your eating into two or three Jethro Bodine feedings.

The plan does assume you are hitting the gym regularly, working every muscle group at least once a week over two or three sessions. Although it would be nice to skip the workouts so you can spend more time at home doing the usual--avoiding chores while watching SportsCenter--without the stimulus of weight training and cardio, you won't be able to achieve the results you're looking for on this or any other diet.

The challenge is yours: Are you ready to beat your caveman genetics and pitch your paunch? Six steps, with a few trips to the gym for good measure, and a sliced-up midsection can be yours.