Men's Health: The Battle for Your Body

VIDEO: How fruits and vegetables are
WATCH Preserving Muscle Mass

The battle goes on whether you're awake or asleep, on the couch or on the treadmill. On one side, the good guy: Muscle. Muscle is like the doorman at your own personal nightclub. It's his job to make you look good, attract the cute girls, and keep out the riffraff. The riffraff, in this case, is a man called Fat.

Fat hates Muscle, and the feeling is mutual. Fat wants to fill your nightclub with all his fat, lazy friends, who will just sit around bumming free drinks, eating all the peanuts at the bar, and scaring the women away. Fat also wants to run Muscle out of town.

You know which side you're rooting for: Muscle burns fat for energy, which is why building and maintaining muscle is the key to losing flab and sculpting a lean, toned body. Muscle boosts metabolism, helping you burn calories day and night. Muscle heightens your testosterone level, keeping aging at bay and your sex drive revving. Muscle helps protect you from heart disease, back pain, arthritis, and depression. Help Muscle win the war against Fat, and you'll triumph over much more than your waistline. The key: firing up your metabolism.

Just what is metabolism? Simply put, it's all the various chemical reactions that happen inside your body 24-7 to keep you alive. Think of your metabolism as your caloric bouncer, ready to throw Fat out of Club You.

Your metabolism isn't an instant-makeover machine, but you can order it to keep an eye out for big fat party crashers and throw them back onto the street. Learn these surprising truths, and you'll help Muscle conquer its flabby nemesis—once and for all.

Truth #1: Burning calories in the gym is (almost) a waste of time

Sure, burning calories is great. But the energy you expend in the gym isn't as big a deal as those LED readouts on the treadmill might make it seem. In fact, we all have three distinct types of "burns" that make up our metabolism. See below.

Burn #1: Basal (Resting) Metabolism -- 60-75%

Your basal metabolic rate, or BMR, accounts for 60 to 75 percent of your overall metabolism. Surprisingly, it represents the calories you burn doing nothing at all. It's fueled by your heart beating, your lungs working to breathe, and even your cells dividing.

Burn #2: Digesive Metabolism -- 10%

This burn results from the thermic effect of food, or TEF. Simply digesting food—converting carbohydrates to sugar and protein to amino acids—typically burns 10 percent of your daily calories. You burn more calories digesting protein than you do digesting carbohydrates and fat—about 25 calories for every 100 consumed, versus zero to 10 for carbs and fat.

Burn #3: Exercise and Movement Metabolism -- 15-30%

This part of your metabolism includes your gym workouts and other physical activities such as jogging or playing softball (called "exercise-activity thermogenesis," or EAT). It also includes your countless incidental movements throughout the day, like turning the pages of a magazine ("non-exercise-activity thermogenesis," or NEAT).

So why is it so hard to lose weight just by exercising? Why do you see so many overweight people in the gym? The answer is simple. Exercise and movement account for only 15 to 30 percent of your fat burn. Up to 85 percent of your calorie burn in a given day has nothing to do with moving your body. But that doesn't mean you should skip the gym--you just need to know how to make exercise work for you. The fact is, exercise can play an important role in preparing Muscle to conquer its greatest threat—Fat, of course.

Truth #2: The fatter you get, the fatter you'll get

Fat doesn't just show up at your door one day, rent a room, and live quietly alone with a couple of cats. Fat loves company. The more fat you open the door to, the harder you'll find it to stop even more fat from inviting itself in. Here's why.

Your BMR—basal (resting) metabolic rate—accounts for the majority of the calories you burn every day. It's determined by a number of factors: your sex, age, and height; your genes (most likely); and your body's ratio of fat to muscle. The problem is, fat slows your calorie burn. Fat is lazy on a metabolic level: It burns barely any calories at all. For your body to support a pound of fat, it needs to burn about 2 calories a day. Muscle, on the other hand, is metabolically very active. At rest, 1 pound of skeletal muscle burns three times as many calories every day just to sustain itself—and the more calories you burn, the more body fat you tend to lose. That's why Fat hates Muscle—because Muscle is constantly burning it off.

So Fat actually fights back, trying to erode Muscle. The main fat culprit is a nasty variety called visceral fat, which resides behind your abdominal muscles and surrounds your internal organs (the viscera). And visceral fat works its mischief by releasing a variety of substances collectively called adipokines. Adipokines include compounds that raise your risks of high blood pressure, diabetes, arterial inflammation, and high blood sugar.

Visceral fat also messes with an important hormone called adiponectin, which regulates metabolism. The more visceral fat you have, the less adiponectin your body releases and the slower your metabolism is. So fat literally begets more fat. In fact, a study in the Journal of Applied Physiology showed that the biologically active molecules that are released from visceral fat can actually degrade muscle quality--which, again, leads to more fat.

The solution? Bigger muscles. In addition to boosting your metabolic rate, muscle mass plays a key role in preventing more common (but no less deadly) conditions such as cardiovascular disease and diabetes. A survey of scientific literature published in the journal Circulation linked the loss of muscle mass to insulin resistance (the main marker of type 2 diabetes), elevated blood lipid levels, and increased body fat, especially visceral fat.

Truth #3: Weight training is the ultimate fat fighter

While muscle burns calories, bigger muscle burns more calories. That's because the physical work you need to do to build and maintain added muscle can have a dramatic effect on your overall metabolismResearch shows that a single weight-training session can spike your calorie burn for up to 39 hours after you lift. (And remember, this doesn't include the calories you burn while you're actually exercising. Think of those as a bonus.)

And the long-term calorie burn you enjoy from building muscle does more than just eliminate extra weight. It specifically targets fat! A study conducted by Jeff S. Volek, Ph.D., R.D., an exercise and nutrition researcher at the University of Connecticut, showed that people who built muscle lost almost 40 percent more fat on restricted-calorie diets than nonexercisers and aerobic exercisers.

Another reason weight training is the ultimate fat fighter: The more muscle you have, the better your body uses the nutrients you consume, and the less likely it is to store your food (even junk food) as fat. See, your muscles store energy (read: calories) in the form of glycogen. When you exercise, your muscles call on that glycogen for fuel. After you exercise, your fat-storing hormones are subdued because your body wants to use incoming carbs to restore the glycogen depleted during your workout. So the carbs you eat after exercise are stored in your muscles, not in your spare tire.

But it gets better: If you complete a high-intensity workout (like the one below), your body will burn calories at an advanced rate for hours afterward, and it'll be desperate for energy to keep your heart beating. Since the food you're eating is being stored in your muscles, your body has to hunt for something else to burn. Guess what that is? Fat. Score another one for Team Muscle.


More from Men's Health:

15 Easy Ways To Rev Up Your Metabolism

7 Worst Weight-Loss Saboteurs

Discover 8 ways to cut the fat without realizing it

Learn 10 ways to lose weight without starving