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Unless you’re one of those rare folks blessed by the fast-metabolism gods, you’d probably like to burn a few more calories than you do – both while at work and at rest. The question is: How?

Metabolism is a mysterious animal, one affected by genetic factors as well as a complex interaction of lifestyle, nutrition and exercise habits. It’s worth understanding, though, because with a well-honed metabolism you can bolster your fat-burning and fitness-training regimens in remarkable ways. And a sluggish metabolism can blunt your most valiant weight-loss efforts.

Interested in optimizing your body’s fat-burning, energy-producing machinery? Start by learning just a little about how your metabolism works. Then take note of the key builders and busters that can work for or against your metabolism in powerful ways.

What Is Metabolism?

In fitness circles, “metabolism” is often used interchangeably with “metabolic rate” to refer to the number of calories you burn in maintaining body functions and fueling your activities. But there’s more to metabolism than just calorie burning. Metabolism also encompasses chemical and physical reactions occurring in every one of your body’s tissues – from using proteins for muscle-building (called anabolism) to breaking down food into the proteins, fats and carbs that your body uses to fuel itself (called catabolism). You need both processes to develop strength and stamina and to build resistance to aging and disease.

What benefits one aspect of metabolism generally benefits the others, says Paul Chek, holistic health practitioner and founder of the Corrective Holistic Exercise Kinesiology (C.H.E.K) Institute in Vista, Calif. ( “Metabolism is like a spider web,” he explains. “You can’t pull on one part of the web without affecting the others.”

Nutrition, exercise and other lifestyle factors, like sleep and stress, can all go a long way toward building or busting your metabolism. But keep in mind that many diseases, including thyroid disorders and diabetes, can interfere with metabolic processes. Talk to your doctor about ruling out such medical conditions if you suspect you might be affected by one, and do not significantly alter your exercise or nutrition program without consulting a health professional.

Metabolism Builders and Busters

In each of the three following categories – fitness, nutrition and lifestyle – we’ve highlighted the top two habits that can either shore up your metabolism or break it down. Metabolism “builders” boost caloric burn, promote anabolic growth or encourage the use of fat as a fuel source. “Busters,” conversely, slow the rate at which your body burns calories and fat – or they create excessive catabolic tissue breakdown, thus hindering fitness progress and, in some cases, contributing to injury or disease.


Different types of exercise enhance your metabolism in different ways. You’ll get the best results by combining them in a balanced program appropriate for your current fitness level.

Builder 1: Heart-rate cardio training plus weightlifting

Heart-rate, or zone-based, cardiovascular training is one of the best metabolic boosters around, says Jeff Zwiefel, vice president of fitness, training and new program development for Life Time Fitness. Exercising in the five different heart-rate zones at different intensities yields unique metabolic benefits, such as increased aerobic capacity, maximized caloric burn and improvements in the way your body burns fat as a fuel source.

You may spend more time training in one zone than another based on your fitness level and specific goals. For the greatest range of metabolic benefits, though, incorporate all zones into your exercise program (unless you have a medical reason not to), either on separate days or in a single workout by using interval training.

But don’t neglect weightlifting and other forms of resistance work that help you build sleek, powerful muscles. For one thing, those muscles make you stronger (and thus make exercise easier). For another, accumulating lean tissue increases your body’s metabolic rate. That’s because, pound for pound, muscle burns more calories than fat.

How much more?

According to a 2001 report published in the Current Opinion in Clinical Nutrition and Metabolic Care, even at rest, muscle tissue is three times more metabolically active than fat, with muscle burning about 6 calories per pound per day compared to fat’s 2. A daily difference of 4 calories per pound may not sound like a lot, but it adds up. Put on 5 pounds of muscle and your body will automatically start burning an extra 30 calories per day. That amounts to about 10,950 per year, which might net you another 3-pound fat loss, thus improving your lean-to-fat ratio and potentially boosting your metabolism even more. Over the course of a few years, this type of increased metabolic activity can make achieving and maintaining your ideal weight far easier.

Does that mean you can just crank on the weights and forget cardio?

No. First, cardio’s heart-health benefits are too good to ignore. Second, cardiovascular exercise typically burns considerably more calories than weight training does, and it eclipses the calories you can burn by merely accumulating lean tissue. For example, a 150-pound person bicycling or jogging at a moderate pace (12 to 14 mph cycling, 5 mph jogging) burns about 360 calories in a half-hour. That same person doing light to moderate weight training will burn 135 calories in the same amount of time, and even if she boosts the intensity for a vigorous weight workout she’s looking at 270 calories – well under the cardio expenditure.

Another reason to do both types of exercise: They both produce a metabolic “afterburn” effect called excess postexercise oxygen consumption (EPOC), which can increase your body’s rate of caloric burn for up to two hours after you exercise (net burn: anywhere from 5 to well over 150 additional calories). The EPOC for cardio and resistance workouts is about the same, assuming intensity and total calorie burn are similar, according to a 2004 report in the Journal of Strength and Conditioning Research. But because cardio generally burns more calories per minute, for workouts of the same time length, cardio has the EPOC advantage.

Builder 2: Exercise variety

Mixing things up keeps your mind motivated, but it also optimizes your caloric burn rate, Chek says. His recipe for a potent metabolic boost: Pick several different aerobic activities, then do three to five minutes of each in circuit fashion. Or at least pick a different activity for each workout. “The idea is to keep your physiology guessing,” he says.

Chek explains that your body is designed to conserve energy, and it does so by becoming more fuel efficient at performing whatever activity you ask of it. The more efficient it becomes, the less energy (read, calories) it uses to perform the same task.

Frequently changing and upgrading your fitness routine keeps your body constantly adapting, so it has to bring its A-game each and every time. The same goes for weight training. Varying exercises, equipment, reps and sets, amount of weight, and pacing will all help keep exercise fresh.

Buster 1: No exercise

Bottom line: Any exercise is better than no exercise. Being sedentary means you miss the immediate metabolic boost of the activity itself, plus the chance to increase your calorie-guzzling muscle tissue. Sit too long, and all your body’s systems slow to a crawl. A sedentary lifestyle also contributes to ill health and depression, which further reduce your energy and make moving even less appealing.

Buster 2: Inadequate exercise recovery

Overtraining is not just something that happens to competitive athletes. It affects people in all gyms,” says Paul Robbins, metabolic specialist for Athletes’ Performance in Tempe, Ariz. If you are exercising intensely on a daily basis, at least one recovery day a week is critical, no matter what your fitness goals are. And you may need more, because the growth-producing, strength-enhancing changes that exercise stimulates occur during rest, not during exercise itself. He notes, “Without time to rest and recuperate, you’ll never be strong enough to hit those training high notes like you should.”


As you develop the nutritional part of your metabolic plan, you’ll want to consider both the “what” and the “when” of your eating habits.

Builder 1: Clean, wholesome food

Optimal metabolism, on a fundamental level, means that your cells are efficient at producing energy and removing toxins, Chek explains. “We tend to focus on getting the right macronutrients for energy production, but we overlook the toxic load of some foods. That’s crucial, though, because any time your body becomes polluted with toxins faster than it can clean itself, the thyroid slows your metabolic rate to allow your cells time to remove the sludge.”

It works like this, he says: Toxic chemicals in foods – like pesticides, herbicides, antibiotics, hormones, highly processed sugars and trans fats – are perceived by your body as stress, and like any other stressor, they trigger your fight-or-flight response, releasing the stress hormone cortisol. Chronically elevated cortisol levels often result in reduced thyroid activity that, in turn, slows metabolism. (For more on stress, see Lifestyle Buster No. 2.)

In the interest of fueling your metabolic fire, feed your body a balanced range of wholesome, natural and nontoxic nutrients in the form of high-quality whole foods. Make vegetables, fruits, whole grains, legumes, nuts and seeds the center of your diet. Include dairy and animal products (fish, poultry, lean beef, eggs) in moderation as they suit you. Choose organic, free-range or wild-caught, locally raised and minimally processed foods whenever possible. Eat more “live” (uncooked) fruits and vegetables to take advantage of their enzymatic activity and nutritional density.

Builder 2: Nutrient intake and timing

Eating smaller, more frequent meals improves digestion, nutrient absorption and thus overall metabolism, according to nutritional biochemist Stephen Cherniske, MS. In fact, in his book The Metabolic Plan: Stay Younger Longer, he writes that “people who consume 2,000 calories a day via grazing tend to lose weight, while those eating the same number of calories at lunch and dinner (as 90 percent of Americans do) tend to gain weight.”

Even if you can manage smaller, frequent meals, choosing a healthy balance of foods can be challenging. And any nutrient gaps left open can cut into your metabolism’s ability to do its job. That’s just one reason why a daily multivitamin is advisable for most.

For active individuals, recovery nutrition is another critical factor in optimizing metabolism. In Nutrient Timing: The Future of Sports Nutrition, authors John Ivy, PhD, and Robert Portman, PhD, describe the 45-minute “metabolic window” immediately following a workout.

During this postexercise period, your body requires the right combination of nutrients to initiate the repair of damaged muscle and replenish muscle glycogen stores. Consuming a 200- to 300-calorie snack with a ratio of 3 or 4 grams of carbs to 1 gram of protein produces optimal results in most people.

A well-designed liquid meal or sports drink is one of the best ways to obtain this postworkout nutrient boost because it’s easily digested and quickly absorbed. But eating half a sandwich, a container of yogurt, some cheese and fruit, or nuts and berries can also do the trick. (See “12 Quick Preworkout and Postworkout Snacks” for well-balanced combinations to support your work.)

Buster 1: Sugar and other simple or refined carbohydrates

Taking in too many refined sugars and carbs puts your body on an energy-draining, metabolism-killing, blood-sugar roller coaster. It also sets you up for diabetes and metabolic syndrome, both of which increase your risk of an early death.

According to a 1999 report from the Center for Science in the Public Interest (CSPI), the average American is scarfing down 64 pounds of added sugar per year from highly refined carbohydrates like table sugar and corn syrup. That’s about 20 teaspoons per day, or 80 grams, not including the sugars found in fruits, vegetables or dairy products. Plus, most refined-flour products – from bagels to pizza dough – turn to sugar very quickly in your system. If you want to build a healthy metabolism, play it safe and aim to eliminate processed sugars and refined carbohydrates at every opportunity.

Buster 2: Lack of water

Many Americans consume more caffeine-laden coffee and soft drinks than they do water. If you’re one of them, “you might as well paste a sign on your forehead, ‘AGING AS FAST AS I CAN,'” Cherniske writes. Caffeine can act as a dehydration-promoting diuretic, he notes, and even slight dehydration wreaks havoc on your metabolism. That’s because water is required for all anabolic repairs, like recovery from exercise or healing from an injury, yet dehydration accelerates catabolic damage.

Precisely how much water we need depends on a variety of dietary and lifestyle factors. But most health experts still agree that for most people, the old standby of 8 to 10 cups (64 to 80 ounces) a day is a good goal. You’ll want to drink more if you regularly work up a sweat. The American College of Sports Medicine recommends about 10 ounces for every 10 to 20 minutes of exercise. (See “How to Hydrate” for hydration guidelines.)


While fitness and nutrition are big pieces of the metabolic puzzle, don’t forget that how you live the rest of your life matters, too.

Builder 1: Sleep

“Just like water, food and air, sleep is a foundational health factor,” Chek says. Sleep is a peak time for growth and repair. When you skimp on shuteye, you make yourself vulnerable to the metabolism-suppressing phenomenon reported by University of Chicago researchers in 1999 in the research journal Lancet: When sleep was restricted to four hours, six nights in a row, young men experienced impaired carbohydrate metabolism, depressed thyrotropin (thyroid-stimulating hormone) concentrations, higher cortisol (a catabolic stress hormone) and a nervous-system response resembling that seen under stress. According to the National Sleep Foundation, most people need at least eight hours of high-quality sleep nightly. (See “The Healing Power of Sleep” for more.)

Builder 2: Activity

Any movement increases your metabolic rate by stimulating muscles and burning calories; even activities like house cleaning or gardening make a difference. The less fit you are, the greater an impact this type of activity has on your metabolism, Chek explains, but any movement throughout the day contributes to both good health and increased caloric burn. The more vigorous, the better. In just 30 minutes, a 150-pound person can burn 135 calories doing housework, and around 225 calories digging in a garden.

Buster 1: Aging

Aging is Mother Nature’s own metabolic buster, and it’s a doozy. Many metabolism-affecting hormones decrease with age, including growth hormone, the adrenal steroid dehydroepiandrosterone (DHEA), and, of course, estrogen and testosterone.

And aging affects metabolically important muscle tissue, too. According to a 2000 report in The Physician and Sportsmedicine, people lose 3 to 6 percent of their muscle mass per decade after age 60, and scientists at the Mayo Clinic in Rochester, Minn., suggest it can start as early as age 40.

Fortunately, all this gloom and doom is not inevitable. We all have metabolism-boosting tools at our disposal, and even though we can’t stop time, Cherniske says that by wielding these tools to enhance anabolic and to limit catabolic metabolism, and by eliminating metabolism busters like lack of activity, we can significantly slow or even temporarily reverse the metabolic decline that usually accompanies aging.

Buster 2: Stress

Of all the lifestyle issues that devastate metabolism, stress is the absolute worst, Chek says. “Your body cannot differentiate between different sources of stress, whether they’re emotional, physical, environmental or hormonal.” And in the long run, they all have the same metabolism-depressing effect.

Once your brain perceives anything as a threat, it initiates your fight-or-flight stress response, which includes the release of the stress hormones epinephrine (more commonly known as adrenaline) and cortisol. When stress becomes chronic, the net result of all this hormonal activity is a metabolism-depressing and vitality-sapping disaster:

Your body, perceiving that it is under attack, shuts down precisely the systems (such as digestion, muscle building and repair) on which healthy metabolism depends. It starts storing up fat for safekeeping, and it begins robbing the stores of bone and muscle tissue that you’ve worked so hard to build.

Stress also tends to encourage metabolism-busting behaviors (like overeating, drinking and skipping workouts) and to dissuade us from metabolism-building ones (like adequate sleep, exercise and good nutrition) that might normally help ameliorate its negative effects. (For more on the effects of stress and what you can do about them, check out “Good Stress, Bad Stress”.)

Build Yourself Up

Mastering your metabolism requires a complex interplay of many factors, but the vast majority of them are well within your realm of influence. Best of all, the adjustments you’ll make in optimizing your metabolism will also positively and powerfully influence your overall health and vitality. And that will make staying in shape easier and more enjoyable for the long haul.

So start now. Even if you pick just one builder to incorporate and one buster to jettison, you’ll soon feel and see the positive results all over your body. And once you do, you’ll be inspired to build even more feel-good metabolic synergy into your health and fitness program – and into your life.

Know Your Numbers

Want to know more about the state of your metabolism? Consider undergoing a metabolic assessment. These simple tests (conducted by capturing your respiration with a mask and feeding the information to a computer) are now available at many leading health clubs, and they take less than 30 minutes to complete.

The gold-standard tests measure your body’s use of oxygen and production of carbon dioxide to determine the rates at which you’re burning fat or carbohydrates for fuel. The following two assessments may cost from $50 to $200 each and may require the purchase of a reusable testing mask for about $40. They can be performed in many major health clubs and will give you the most accurate picture of your current metabolic state.

  • Resting metabolism. Measuring resting metabolism takes 15 to 20 minutes; you simply sit in a chair and breathe into a mask. Your total caloric expenditure is figured as a combination of your resting metabolic rate (RMR) and lifestyle activities. RMR tells you the number of calories burned just by keeping your internal organs (brain, heart, lungs, kidneys, etc.) functioning. Then it’s adjusted for your lifestyle-activity level. Combining your RMR with the calories you need to perform daily activities gives an idea of how many calories you should consume to maintain your weight.
  • Exercising metabolism. Exercising metabolism tests vary in length according to your level of fitness. They require you to exercise at a range of intensities – usually by walking or jogging on a treadmill – while breathing into a mask. The mask is hooked up to equipment that measures your body’s use of oxygen and carbon dioxide. A computer then calculates your body’s ability to burn calories and fat at various exercise intensities. You wind up with a report (your own personal metabolic profile) that shows which exercise intensities produce the greatest caloric- and fat-burn rates, and which produce the best cardio-fitness gains.

See our “Fitness Testing” series for more info on various types of fitness testing and how they can help you exercise more efficiently. Or inquire at your health club’s training desk.

This article has been updated. It originally appeared in the May 2006 issue of Experience Life.

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