Here's a bet you can't lose. Challenge a friend that you can make better progress toward a set of six-pack abs over the next month than he can. The catch: You can't do any ab exercises, but he can't change his diet.

Does he want to put his abs through a two-sessions-per-day split? Fine. Does he want to do 1,000 sit-ups every morning with a couple of electrostimulation devices strapped on for good measure? Go for it. Meanwhile, your only workout will be a simple calorie-controlled program that's heavy on vegetables, generous on protein, and light on starchy carbs. You'll beat him without a single crunch.

Popping your abs is almost completely a function of diet. All the resistance exercise in the world can't put ripples in your porridge belly if you're eating more calories than you're burning.

That's not to say crunches don't have their part to play. The perfect formula includes a cardio plan to dump extra calories, a balanced resistance-training program that shapes your mounds of mush into six neat compartments (or eight, if your DNA is a bit freaky), and a diet that trims body fat. We've given you the first two ingredients elsewhere in this issue (see "Power Walking," page 40, and Personal Trainer, page 88). Here is the third, and what many experts believe to be the most important, component to dropping notches in that belt.

THE 90/10 APPROACH

One thing that's not on the menu is deprivation. In the first week of our eating plan, designed by nutritionist Joy Bauer, M.S., R.D., author of The Complete Idiot's Guide to Total Nutrition and, her latest book, The 90/10 Weight-Loss Plan, you eat a healthy breakfast and don't count a single calorie for the rest of the day. In Week 2, you add a healthy lunch. In Week 3, you commit to breakfast, lunch and a low-fat, high-protein snack. Week 4 requires an all-out effort, yet you won't have to swear off your favorite foods entirely. Our plan breaks you of your poor eating habits slowly and surely.

"This is a sane, smart way to eat," says Bauer. "Eat 90 percent healthy and 10 percent fun. That 10 percent removes the deprivation aspect of most diets, and it makes people feel like they don't have to be 100 percent perfect all the time. It's about moderation, feeling normal, feeling in control, and it helps people forgive themselves if they're less than perfect."

And, as Bauer explains, this is no hit-it-and-quit-it short-term fix, but rather a program that "eases you into how you should be eating for the rest of your life. And if you want to jump right to Week 3, more power to you. But if you want to do it in steps, the small motions add up to huge triumphs."

To start, go to "Week 1: Breakfast" and follow the instructions. In the second week, you'll follow the instructions from Weeks 1 and 2. The meals are targeted at a 170-pound guy looking to lose body fat. If you're 140 pounds or less, drop 200 to 300 calories from the diet plan (lose the fruit at breakfast and cut another 100 to 200 calories by eliminating the pita bread, potato or brown rice from your dinner). If you're at or above 200 pounds, add 200 to 300 calories by eating an extra serving of fruit at any point in your day and increasing your lean-protein portions (skinless chicken breast, protein shake, turkey breast or grilled fish) at lunch and dinner.

Make the commitment to take on one week at a time, and before you know it you'll be spending a Sunday afternoon shopping for a new belt and showing off your six-pack.

WEEK 1: BREAKFAST

Instructions: In the first seven days you need only concentrate on one thing: eating a healthy breakfast every day, choosing one of the six options below.

You don't have to sample all the different breakfasts (and this rule holds true for the upcoming meals as well). Choose one you like and eat it all seven days, or pick two or three and rotate them. Just make sure not to go over the recommended portion sizes.

Also, include one fruit serving with whatever breakfast you choose: one cup of berries, melon or pineapple; a fruit salad; a whole pink grapefruit; two small plums; one peach, apple, orange or banana; or two tablespoons of raisins. As for beverages, skip the fruit juice. Instead, drink lots of water, a cup of skim or soy milk, or a cup of black coffee or tea.

BREAKFAST OPTIONS

1. A bowl of high-fiber cereal with one cup of skim milk. Choose a cereal that has more than five grams of fiber per serving, such as Kashi Good Friends, Kashi Go Lean, bran flakes or shredded wheat Sorry, Count Chocula doesn't make the cut.

Totals: 330 calories, 68g carbs, 11g protein, 1.5g fat

2. Whole-grain English muffin with tomato slices and two pieces of melted low-fat cheese. For muffins, try Matthews or Thomas'. For the cheese, try a fresh Jarlsberg/muenster light or Alpine Lace.

Totals: 280 calories, 46g carbs, 16g protein, 4g fat

3. Five-egg-white vegetable omelet (onion, tomato and pepper). You can use one whole egg plus four egg whites, or a small container of egg substitute. Use nonstick cooking spray to fry them up in a pan. With the eggs, have two slices of dry whole-wheat toast or a dry whole-grain English muffin.

Totals: 300 calories, 47g carbs, 25g protein, 3g fat

4. One cup of low-fat or nonfat cottage cheese with two tablespoons of crunchy cereal, wheat germ or ground flaxseeds. You can use your fruit serving as a sweetener for the cottage cheese.

Totals: 300 calories, 36g carbs, 30g protein, 3.5g fat

5. Unsweetened oatmeal or steel oats. Mix a half-cup of oatmeal with water, skim or soy milk. Get your fruit serving by adding two tablespoons of raisins or one cup of berries.

Totals: 250 calories, 45g carbs, 11g protein, 3g fat

6. Protein shake. In a blender, mix one 100-calorie scoop of protein powder (any brand will do) with one cup of skim milk, half a banana, one cup of berries, and ice cubes.

Totals: 340 calories, 60g carbs, 32g protein, 1.5g fat

Gut Check: After one week you should be able to slide a thumb comfortably into your waistband.

WEEK 2: LUNCH

Instructions: In the second week, you'll continue your breakfast routine while starting to eat a healthy lunch. Here's one added twist: Drink two glasses of water (at least 16 ounces total) before each meal. "Water fills up abdominal space to make you full faster, and it gets you into the mind-set that you're on a diet," says Bauer.

LUNCH OPTIONS

1. Soup and chicken or fish. A bowl of any non-creamy, vegetable-based soup, such as minestrone, vegetable barley or tomato (try Progresso soups, but no crackers), with six ounces of grilled, skinless chicken breast or fish.

Totals: 500 calories, 58g carbs, 54g protein, 6g fat

2. Sandwich and salad. Four ounces of lean turkey breast, grilled chicken breast, lean ham, or tuna salad on two slices of whole-grain bread, oat-bran bread or pita bread (no rolls, no bagels). Use mustard, ketchup, barbecue sauce or low-fat mayo to add flavor. Also, have a side salad with two tablespoons of low-fat dressing, or with one tablespoon of vinaigrette dressing, one teaspoon of olive oil and as much vinegar and lemon juice as you wish.

Totals: 500 calories, 57g carbs, 43g protein, 12g fat

3. A large salad and a slice of whole-grain bread. Top the greens with four ounces of a lean protein, such as plain tuna, grilled salmon, shrimp, skinless chicken breast or turkey breast. Also include a half-cup of chickpeas, beans or corn. Flavor with two teaspoons of olive oil and lots of vinegar, or two to four tablespoons of a low-fat dressing.

Totals: 500 calories, 65g carbs, 46g protein, 8g fat

4. Five-egg-white omelet, with any vegetable combination, and two slices of whole-wheat toast. If you wish, you can add a slice of low-fat cheese and a fresh fruit salad on the side.

Totals: 500 calories; 80g carbs, 37g protein, 7g fat

5. A plain hamburger, turkey burger or veggie burger. Have as many sliced tomatoes as you'd like and an orange or a grapefruit on the side, but no bun and no fries.

Totals (for a beef burger): 500 calories, 45g carbs, 25g protein, 20g fat

6. A baked potato with steamed chopped broccoli, a half-cup of shredded low-fat cheese and one cup of vegetable soup. If you're eating out, you can have three tablespoons of Parmesan cheese, since most restaurants aren't likely to have low-fat cheese.

Totals: 500 calories, 75g carbs, 27g protein, 8g fat

Gut Check: After two weeks you should be very close to moving up one hole tighter in your belt.

WEEK 3: HIGH-ENERGY AFTERNOON SNACKS

Instructions: In Week 3, your healthy breakfast and lunch are now supplemented with a smart afternoon snack. Although this plan allows you to have anything you want for dinner, try not to overeat. At this point you want to ready yourself for the upcoming Week 4. As you do before lunch, drink two glasses of water before snacking.

AFTERNOON SNACK OPTIONS

* One handful of nuts (any type, except macadamia)

Totals: 200 calories, 9g carbs, 6g protein, 17g fat