Facts and myths about metabolism

Separate fact from fiction and use it in your weight loss plan.

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Your body burns more calories when digesting cold drinks and foods.

True. But before you get a headache from eating ice cream, consider this: “A small difference in calories won’t make a huge difference in your diet,” explains Madeline Fernstrom, MD, PhD, founder and director of the UPMC Weight Management Center in Pittsburgh. On the other hand, various studies have shown that drinking five to six glasses of cold water a day can help you burn an extra 10 calories, which translates to about a pound of extra weight loss per year without much effort.

Tip: Although the metabolic benefits are small, drinking non-alcoholic beverages such as tea, water, and coffee will still increase your calorie-burning potential.

Drinking enough water will help you burn more calories.

Truth: All of your body's chemical reactions, including metabolism, depend on water. If you're dehydrated, you may burn 2 percent fewer calories, according to University of Utah researchers who monitored the metabolic rates of 10 adults as they drank varying amounts of water throughout the day. In the study, participants who drank eight to 12 glasses of water a day had higher metabolic rates than those who drank four glasses.

Tip: If your urine is darker than straw yellow, it may mean you are not drinking enough fluids. Try drinking one glass of water before each meal to stay hydrated.

Dieting lowers your resting metabolic rate, making it harder to lose weight

True. For every pound you lose, your body burns 2-10 fewer calories per day. Lose 10 pounds, and you'll need to eat 20-100 fewer calories to maintain a lean physique, not including exercise. However, you can prevent your metabolism from slowing down while you're losing weight. One way is to lose fat but maintain muscle mass. You can do this by cutting calories and doing aerobic and resistance exercise. Crash diets (less than 1,000 calories per day) can cause serious muscle loss.

Tip: Lose weight by cutting out 250 calories a day and burning 250 calories a day through exercise. This will help you maintain and even gain muscle mass while losing a large percentage of fat.

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Spicy food will speed up your metabolism

True. Capsaicin, the bioactive compound that gives chili peppers their spicy flavor, can boost your metabolism, as well as make you feel full and reduce hunger. Research shows that eating 1 tablespoon of chopped red or green chili peppers, which contain 30 milligrams of capsaicin, causes a temporary 23% increase in metabolism. Another study gave participants 0.9 grams of red pepper in capsule form or as a natural component of tomato juice before each meal. The researchers found that after just two days, participants’ total calorie intake decreased by 10% and 16%, respectively, and they also felt full.

Tip: Sprinkle red pepper flakes into pasta, Mexican chili, or stews; fresh chilies can be added to sauces and as a fiery spice to many other dishes.

Eating plenty of protein will speed up your metabolism.

Truth: Protein has a more intense metabolic impact than fats and carbs because your body uses more energy to process it, a phenomenon known as the thermic effect of food. Research shows that you can burn twice as many calories digesting protein as you can digesting carbs. In a typical diet, 14 percent of your calories should come from protein. Double that (and cut back on carbs to avoid unnecessary calories), and you can burn an extra 150 to 200 calories a day, explains Donald Layman, MD, PhD, professor of nutrition at the University of Illinois.

Tip: To reap the full benefits of protein, aim for 10 to 20 grams of protein with each meal, says Hickey. Try an 8-ounce cup of low-fat, plain yogurt for breakfast (about 13 grams), ½ cup of hummus for lunch (about 10 grams), and a 3-ounce salmon fillet for dinner (about 17 grams).

Eating grapefruit before every meal speeds up your metabolism

False. Grapefruit won’t do wonders for your metabolism, but it can help you shed pounds. According to a study published in the Journal of Medical Nutrition, eating half a grapefruit before meals helped participants lose about 4 pounds over 12 weeks. The reason: The fiber and water in grapefruit fill you up, so you eat less at your next meal.

Tip: Instead of soup or salad, drink juice or eat fresh fruit, such as half a grapefruit or tangerine, before eating your main meal.

Lifting weights increases metabolism more than cardio

True. When you do enough resistance training to gain 3 pounds of muscle, you increase your calorie burn by 6 to 8 percent, meaning you burn about 100 extra calories per day. Aerobic exercise, on the other hand, doesn’t increase lean muscle mass very much. “The best way to build muscle is through resistance training,” says Ryan D. Andrews, R.D., a Colorado-based strength training specialist and dietitian.

Tip: “You want to focus on exercises that involve your largest muscles and use two-part movements, as these will help you build more lean muscle mass,” says Andrews. His favorites include squats, push-ups, and any exercise that combines upper- and lower-body movements. For more on metabolism-boosting strength training, visit prevention.com/burnfat.

Celery helps reduce calories because it takes more calories to digest than it takes in.

False. The thermic effect of food does cause your body to burn calories as it digests food and drinks. But this process only uses up to 30% of the calories you eat (for example, digesting protein requires more calories than fat and carbohydrates; see question #5). A medium-sized stick of celery contains only about 6 calories; its thermic effect is half a calorie. In fact, calorie-saving foods are just a figment of our imagination.

Tip: Add celery to salads, stews and soups as a low-calorie but filling product; but remember that it cannot magically rid you of your weight problems. However, celery is a healthy product: it contains phthalides, components that lower blood pressure.

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Tea Speeds Up Natural Calorie Burning

True. The catechins in green and oolong tea may speed up the body’s fat-burning process. A study of Japanese women compared the effects of drinking green tea, oolong tea, and water. Just one large cup of oolong tea increased calorie burning by 10%, and a couple of hours later, that number increased by another 1½ times. Green tea increased metabolism by 4% over 1½ hours. Other studies show that drinking 2-4 cups of green or oolong tea per day (containing about 375-675 mg of catechins) can cause you to burn an extra 50 calories per day—the equivalent of losing 5 pounds in a year.

Tip: Try replacing your morning cup of coffee with a cup of green or red tea, which also contain the caffeine needed to speed up your metabolism. Instead of milk or sweetener, add a squeeze of lemon to your tea, which will help your body absorb more catechins.

Increased appetite during PMS is associated with the acceleration of metabolism before menstruation

True. If there's one upside to PMS, it's that our resting metabolism can speed up during a period of the menstrual cycle called the luteal phase (the day after ovulation until the first day of your period). The hormonal-induced metabolic surge can equal 300 calories a day, which is why our appetite increases during this phase.

Tip: Write down what you eat the week before and the week after your period. Try to stick to your diet for the entire month so you can benefit from the calorie-burning hormones. If you do give in to your cravings, try to keep portion sizes under control.

If you are limited in time, exercise at a higher intensity to achieve a metabolic boost.

True. People who exercise at very high intensities experience a higher resting metabolic rate after exercise, and this increase is more intense and lasts longer than with low- and moderate-intensity exercise. Add energy to your exercise, and you'll burn at least 10 percent of your total calories about an hour after exercise. If you do a 4-mile walk/run combination (about 400 calories) instead of just walking, you'll burn an extra 40 calories over the next few hours.

Tip: Incorporate periods of high speed increases into your training. Gradually work up to 2-minute intervals 3 days a week.