Credit: Corey Jenkins / Getty Images

You're not fat. Fat is the guy spilling over the armrest on the plane. Fat is your college buddy who lives on fries and hasn't seen the inside of a gym since Rocky V. You could lose 10 pounds, but who couldn't? You already eat well and work out, so you imagine that dropping the last few requires a kind of deprivation you're not willing to endure. But does it? Perhaps it wouldn't take such a sacrifice to get down to your baseline, or the way you looked at 25. Could you get there without exercising for hours and shunning alcohol? The short answer is yes, if you're willing to work hard for six weeks. It's a numbers game that involves counting calories, structuring workouts, and even clocking sitting time. But the result is guaranteed fat loss. Unlike gimmicky programs, this plan is based on science proved to help you shed fat and not regain it the moment you return to normal. You may even lower your blood pressure and cholesterol along the way. And if you think of it as a game, you're more likely to succeed. Follow these rules for six weeks and you'll be in the place you want.

1. The 200 Calories Rule
No matter what you hear, you can't ignore basic science: Weight loss comes from consuming fewer calories than you burn. But it's not true that the less you eat, the faster you'll lose weight. Creating a large calorie deficit only slows metabolism and triggers hunger. So how many calories should you cut? Research shows that eating 200 fewer calories than you need causes weight loss without affecting metabolism. A Tufts University study found that people who consumed 200 fewer calories a day than they burned lost as much as people who ate 750 fewer calories a day. To eat 200 fewer calories — about 20 potato chips — figure out how much food you need to sustain your current weight by downloading an app like MyNetDiary or visiting sites, like, with calculators that compute daily requirements. For example, an active 40-year-old man needs about 2,800 calories a day to maintain his weight. Subtract 200 from the number for your daily target. To hit that target, you'll have to count calories in all you eat and drink for seven days, which is annoying but lets you approximate after that. There's no need to weigh foods: Just read labels and look up meat, fruit, and veggies on an app or website. Be sure to calculate snacks and alcoholic drinks. And it'll be a lot easier than you think, in part because you'll rotate through the same meals.

2. Boring Diets Are Better 
The majority of successful dieters eat fewer types of foods than the average person. "Eating repetitively helps people control calories," says J. Graham Thomas, a professor at Brown University's Weight Control & Diabetes Research Center. When you have to eat the same meals, you're less likely to make your dinners out of snacks. Eating repetitively also limits selection, which is what fad diets do by ruling out food groups (Atkins) or encouraging only one type of food (grapefruit diet). How to do it? Choose two breakfasts, three lunches, and four dinners that you can rotate for the next six weeks. Snack on what you want, but figure those calories into your daily target. If you want to drink beer (150 calories per can) or can't live without Oreos (150 calories for three), work those calories into your plan without exceeding your limit.

3. Prioritize Protein
The average adult male gets 16 percent of his daily calories from protein. Try to bump that up to 30 percent. "Protein helps you feel full longer," says Tavis Piattoly, team dietitian for the New Orleans Saints. "When you eat high-protein meals, your desire to eat one to two hours later is basically eliminated." Choose meat, poultry, seafood, beans, eggs, dairy, nuts, and seeds; the leaner the selection, the more calories you'll save. Smart choices include round beef, sirloin, and ground beef with 10 percent or less fat; chicken or turkey breast without skin; pork or lamb tenderloin, loin chops, and leg; and low-fat yogurt, milk, and cheese. All seafood and nuts contain heart-healthy fats. What does a 30 percent protein meal look like? All dishes in our Nine-Meal Plan (below) hit the mark. When eating at home or out, use apps or sites to identify high-protein dishes.

4. Aim to Burn 500 Calories Every Time You Exercise
Studies suggest that people are more likely to exercise regularly if they have a specific goal in mind when working out. So for the next six weeks, your goal is to burn 500 calories every time you exercise and to do it three times a week. A 180-pound guy can burn 500 calories running at an 8.5-minute-mile pace for 30 minutes, swimming moderately for 60 minutes, or walking moderately for 90 minutes. Remember, as long as you burn 500 calories per session, it doesn't matter which type of activity you do.

5 Lift More Weights
A common weight-loss mistake is to prioritize aerobic exercise over weightlifting. You'll shed fat faster — and be able to keep it off — by combining cardio with weights. "Weightlifting increases lean body mass, which increases metabolism and the number of calories your body can burn," says John Berardi, author of The Metabolism Advantage. In other words, lifting increases muscle, and since muscle burns more calories than fat, the more muscle you have, the more energy your body will eat up at rest. "Muscle is like an engine," says David Edwards, a New York City–based trainer. "The bigger your engine, the more fuel you burn." Increasing muscle size in six weeks' time means lifting heavy weights, but not all that often. Hit the gym three times a week for 30 minutes, and do three sets of 10 reps each of bodybuilding exercises that work the large muscle groups: cable-lat rows, machine leg extensions, bench presses, machine leg curls, dumbbell shoulder presses, and machine calf raises. If you hate the gym or don't have time for three sessions, substitute weight workouts with pull-ups, step-ups, crunches, single-leg squats, and inverted bodyweight shoulder presses at home. Don't get tripped up by the seeming contradiction that gaining muscle, which weighs more than fat, will make it difficult to budge the scale. As long as you maintain a 200-calorie deficit, you'll lose weight.

6 Never Sit for More Than 30 minutes
It's not enough to exercise more: You also have to sit less. Research suggests that the more people sit, the fatter they are, regardless of exercise. "There's actually more potential to burn calories in everyday activities than in the 30 minutes a day you spend working out," says Robert Portman, a co-author of Hardwired for Fitness. "But you can't exploit that calorie-burning potential if you're always sitting." Sitting less and increasing incidental activity can add up to hundreds of extra calories burned — and more pounds lost. For the next six weeks, don't sit for more than 30 minutes at a time. Set an alarm, and if you've been sitting for more than that, get up to make calls on your mobile, or walk to talk to a colleague instead of e-mailing.

The Nine-Meal Plan
Eating repetitively limits choices, reduces cravings, and makes counting calories easier. Rotate these meals, recalculating calories with substitutions, or use the plan as a template to create your own dishes. When possible, opt for high-protein, low-calorie foods. Chains like Subway and McDonald's post calorie counts for all selections and feature low-cal options.

Breakfast Wrap • 1 whole-wheat tortilla • 4–6 egg whites • 1 cup red peppers, onions, or other ­vegetables sautéed in olive-oil spray • 1 oz shredded reduced-fat cheese: 324 calories

High-Protein Cereal
with skim milk • 2 cups Kashi GoLean (or similar cereal that contains 10 or more grams of protein and roughly 140 calories per cup) • 1 cup skim milk: 366 calories

Turkey Sandwich • 2 slices high-protein bread (preferably sprouted grain) • 3 oz lean turkey breast • mustard • onion, lettuce, tomato: 342 calories

Chicken Burrito • 1 whole-wheat tortilla • 1 grilled chicken breast • 1/2 cup black beans • 1/2 cup peppers and onions, grilled • 3 tbsp avocado, mashed • tomato salsa: 485 calories

Tuna Melt • 1 slice whole-wheat bread • 2 oz chunk light tuna • 1 tbsp mayonnaise • diced onions • tomato slices • 1 slice reduced-fat cheese: 281 calories

Salmon, Brown Rice, and Snow Peas • 4 oz salmon filet, broiled or baked • 2/3 cup brown rice or quinoa • 1/2 cup snow peas, steamed: 480 calories

Chicken and Broccoli Grill • 1 cup ­broccoli, sautéed in olive-
oil spray • 1 chicken breast, sautéed in olive-
oil spray • soy sauce • 1/2 cup brown rice: 374 calories

Pork Tenderloin, Sweet Potato, and Swiss Chard • 4 oz pork tenderloin, roasted • 1/2 cup sweet potatoes, roasted • 1 cup Swiss chard, steamed: 382 calories

Turkey Meatloaf, Black Bean and Corn Salad • 6 oz meatloaf, made with lean ground turkey • 1/2 cup black bean and corn salad: 444 calories