Book Excerpt: The Abs Diet: The Six-Week Plan to Flatten Your Stomach and Keep You Lean for Life

Changing the Way You Exercise

Have you ever seen a gym at rush hour? Everyone hovers around the treadmills, elliptical trainers, and stationary bikes. Signs warn you of 20-minute maximums so that the next sweat seeker can have his turn. It seems like everyone wants a cardiovascular, aerobic workout. The more you sweat, the more calories you burn, the more weight you lose, right? In a way, yes, the headphone-and-Lycra set is right. Cardiovascular exercise -- steady-state endurance exercises, like running, biking, and swimming -- burns a lot of calories. In fact, it often burns more than other forms of exercise like strength training or trendier workouts like yoga or Pilates. But when it comes to weight control, aerobic exercise is more overrated than the fall TV lineup. Why? For one reason: Aerobic exercise builds little (if any) muscle -- and muscle is the key component of a speedy metabolism. Muscle eats fat; again, add 1 pound of muscle, and your body burns up to an additional 50 calories a day just to keep that muscle alive. Add 6 pounds of muscle, and suddenly you're burning up to 300 more calories each day just by sitting still.

Here's the problem with low-intensity aerobic exercise. Just like a car can't run without gas or a kite can't fly without wind, a body can't function without food. It's the fuel that helps you run, lift, and have the legs to make love all night long. Generally, during exercise, your body calls upon glycogen (the stored form of carbohydrate in muscles and the liver), fat, and in some cases protein. When you're doing low-intensity aerobic exercise like jogging, your body primarily uses fat and glycogen (carbohydrates) for fuel. When it continues at longer periods (20 minutes or more), your body drifts into depletion: You exhaust your first-tier energy sources (your glycogen stores), and your body hunts around for the easiest source of energy it can find -- protein. Your body actually begins to eat up muscle tissue, converting the protein stored in your muscles into energy you need to keep going. Once your body reaches that plateau, it burns up 5 to 6 grams of protein for every 30 minutes of ongoing exercise. (That's roughly the amount of protein you'll find in a hard-boiled egg.) By burning protein, you're not only missing an opportunity to burn fat but also losing all-important and powerful muscle. So aerobic exercise actually decreases muscle mass. Decreased muscle mass ultimately slows down your metabolism, making it easier for you to gain weight.

Now here's an even more shocking fact: When early studies compared cardiovascular exercise to weight training, researchers learned that those who engaged in aerobic activities burned more calories during exercise than those who tossed around iron. You'd assume, then, that aerobic exercise was the way to go. But that's not the end of the story.

It turns out that while lifters didn't burn as many calories during their workouts as the folks who ran or biked, they burned far more calories over the course of the next several hours. This phenomenon is known as the afterburn -- the additional calories your body burns off in the hours and days after a workout. When researchers looked at the metabolic increases after exercise, they found that the increased metabolic effect of aerobics lasted only 30 to 60 minutes. The effects of weight training lasted as long as 48 hours. That's 48 hours during which the body was burning additional fat. Over the long term, both groups lost weight, but those who practiced strength training lost only fat, while the runners and bikers lost muscle mass as well. The message: Aerobic exercise essentially burns only at the time of the workout. Strength training burns calories long after you leave the gym, while you sleep, and maybe all the way until your next workout. Plus, the extra muscle you build through strength training means that in the long term, your body keeps burning calories at rest just to keep that new muscle alive.

That raises a question. What aspect of strength training creates the long afterbu
? Most likely, it's the process of muscle repair. Weight lifting causes your muscle tissues to break down and rebuild themselves at a higher rate than normal. (Muscles are always breaking down and rebuilding; strength training simply accelerates the process.) That breakdown and rebuilding takes a lot of energy and could be what accounts for the long period of calorie burning. In fact, a 2001 Finnish study found that protein synthesis (the process that builds bigger muscles) increases 21 percent 3 hours after a workout.

The good news is that you don't have to lift like a linebacker to see the results. A recent Ohio University study found that a short but hard workout had the same effect as longer workouts. Using a circuit of three exercises in a row for 31 minutes, the subjects were still burning more calories than normal 38 hours after the workout. (The Abs Diet Workout is designed along similar principles, to mimic these results.)

As I said earlier, building muscle increases your metabolism so much that you burn up to 50 calories per day per pound of muscle you have. The more muscle you have, the easier it is for you to lose fat. That's why one of the components of the plan includes an exercise program that will help you add the muscle you need to burn fat and reshape your body. And it also points to one of the reasons why you should deemphasize cardiovascular, aerobic exercise if you want to lose fat: because it depletes your body's store of fat-burning muscle.

Now, before you think I'm some sort of anti-aerobics fanatic, let me clarify a few things: I run almost daily, and I've even completed the New York City Marathon. Aerobic exercise burns calories, it helps control stress, and it improves your cardiovascular fitness. It also helps lower blood pressure and improve your cholesterol profile. If your choice is aerobic exercise or no exercise, for Pete's sake get out there and run. But when it comes to long-term weight management, I'll take gym iron over road rubber any day.

Reprinted from: The Abs Diet: The Six-Week Plan to Flatten Your Stomach and Keep You Lean for Life by David Zinczenko with Ted Spiker © 2004 Rodale Inc. Permission granted by Rodale, Inc., Emmaus, PA 18098. Available wherever books are sold or directly from the publisher by calling (800) 848-4735 or visit their website at www.rodalestore.com

Copyright © 2004 Rodale Inc.