Maybe you've had sand kicked in your face. Maybe you've lost one too many attainable women to beefier guys. Or maybe you've read so much about weight loss that actually admitting you want to gain weight is a societal taboo. Whatever the reason, you want to bulk up. Now.

But forget about your alleged high-revving metabolism, says Doug Kalman, R.D., director of nutrition at Miami Research Associates. "Most lean men who can't gain muscle weight are simply eating and exercising the wrong way," he says.

MEN'S HEALTH RECOMMENDS

Here's your fix: Follow these 10 principles to pack on as much as a pound of size.

Maximize Muscle Building
The more protein your body stores—in a process called protein synthesis—the larger your muscles grow. But your body is constantly draining its protein reserves for other uses—making hormones, for instance. The result is less protein available for muscle building. To counteract that, you need to "build and store new proteins faster than your body breaks down old proteins," says Michael Houston, Ph.D., a professor of nutrition at Virginia Tech University.

Eat Meat
Shoot for about 1 gram of protein per pound of body weight, which is roughly the maximum amount your body can use in a day, according to a landmark study in the Journal of Applied Physiology. (For example, a 160-pound man should consume 160 grams of protein a day—the amount he'd get from an 8-ounce chicken breast, 1 cup of cottage cheese, a roast-beef sandwich, two eggs, a glass of milk, and 2 ounces of peanuts.) Split the rest of your daily calories equally between carbohydrates and fats.

Eat More
In addition to adequate protein, you need more calories. Use the following formula to calculate the number you need to take in daily to gain 1 pound a week. (Give yourself 2 weeks for results to show up on the bathroom scale. If you haven't gained by then, increase your calories by 500 a day.)

A. Your weight in pounds.
B. Multiply A by 12 to get your basic calorie needs.
C. Multiply B by 1.6 to estimate your resting metabolic rate (calorie burn without factoring in exercise.
D. Strength training: Multiply the number of minutes you lift weights per week by 5.
E. Aerobic training: Multiply the number of minutes per week that you run, cycle, and play sports by 8.
F. Add D and E, and divide by 7.
G. Add C and F to get your daily calorie needs.
H. Add 500 to G. This is your estimated daily calorie needs to gain 1 pound a week.

Work Your Biggest Muscles
If you're a beginner, just about any workout will be intense enough to increase protein synthesis. But if you've been lifting for a while, you'll build the most muscle quickest if you focus on the large muscle groups, like the chest, back, and legs. Add squats, deadlifts, pullups, bent-over rows, bench presses, dips, and military presses to your workout. Do two or three sets of eight to 12 repetitions, with about 60 seconds' rest between sets.

Have a Stiff Drink
A 2001 study at the University of Texas found that lifters who drank a shake containing amino acids and carbohydrates before working out increased their protein synthesis more than lifters who drank the same shake after exercising. The shake contained 6 grams of essential amino acids—the muscle-building blocks of protein—and 35 grams of carbohydrates.

"Since exercise increases bloodflow to your working tissues, drinking a carbohydrate-protein mixture before your workout may lead to greater uptake of the amino acids in your muscles," says Kevin Tipton, Ph.D., an exercise and nutrition researcher at the University of Texas in Galveston.

For your shake, you'll need about 20 grams of protein—usually about one scoop of a whey-protein powder. Can't stomach protein drinks? You can get the same nutrients from a sandwich made with 4 ounces of deli turkey and a slice of American cheese on whole wheat bread.

But a drink is better. "Liquid meals are absorbed faster," says Kalman. So tough it out. Drink one 30 to 60 minutes before your workout.

Lift Every Other Day
Do a full-body workout followed by a day of rest. Studies show that a challenging weight workout increases protein synthesis for up to 48 hours immediately after your exercise session. "Your muscles grow when you're resting, not when you're working out," says Michael Mejia, C.S.C.S., Men's Health exercise advisor and a former skinny guy who packed on 40 pounds of muscle using this very program.

Down Carbs After Your Workout
Research shows that you'll rebuild muscle faster on your rest days if you feed your body carbohydrates. "Post-workout meals with carbs increase your insulin levels," which, in turn, slows the rate of protein breakdown, says Kalman. Have a banana, a sports drink, a peanut-butter sandwich.

Eat Every 3 Hours
"If you don't eat often enough, you can limit the rate at which your body builds new proteins," says Houston. Take the number of calories you need in a day and divide by six. That's roughly the number you should eat at each meal. Make sure you consume some protein—around 20 grams—every 3 hours.

Make One Snack Ice Cream
Have a bowl of ice cream (any kind) 2 hours after your workout. According to a study in the American Journal of Clinical Nutrition, this snack triggers a surge of insulin better than most foods do. And that'll put a damper on post-workout protein breakdown.

Have Some Milk Before Bed
Eat a combination of carbohydrates and protein 30 minutes before you go to bed. The calories are more likely to stick with you during sleep and reduce protein breakdown in your muscles, says Kalman. Try a cup of raisin bran with a cup of skim milk or a cup of cottage cheese and a small bowl of fruit. Eat again as soon as you wake up. "The more diligent you are, the better results you'll get," says Kalman.

Credit goes to: Gain a Pound of Size Every Week