All About Calories, Your Body's Fuel

You take them in and burn them off—how to strike a good balance?

Everything you eat—from licorice to pork chops to skim milk—contains calories. And everything you do—from sleeping to running a marathon —burns calories. But what exactly is a calorie, and how does it work?

Put simply, calories are your body’s gasoline. “Just as your car needs about a gallon of gas to drive 25 miles, you need a certain number of calories to generate enough energy to make it through the day,” says registered dietitian Mildred Bentler of Lehigh Valley Hospital and Health Network. How many you need depends on your age and activity level, but for most adults the answer is between 1,500 and 3,000 calories daily. Active people need more, because their bodies “drive” farther.

As we all know, some types of gasoline are more high-powered than others, and the same is true of the calories in food. (A 200-calorie veggie omelet acts very differently in your body than a 200-calorie candy bar!) There are calories in protein, carbohydrates and fat, and you need all three to keep your engine running smoothly—but it’s important to get the right mix:

Protein should make up about 20 percent of your calorie intake. Your body needs protein to repair cells. Good sources are lean meats (such as chicken and fish), beans, lowfat dairy products and eggs.

Carbohydrates should make up about 50 percent of your calorie intake. Carbohydrates fuel your daily functioning. Healthy sources are whole grains, fruits, vegetables and legumes.

Fat should make up no more than 30 percent of your calorie intake. You need it for energy storage and to insulate your tissues, among other things. Healthy (monounsaturated and polyunsaturated) sources include canola, corn, flaxseed and olive oils; avocado; nuts; and fatty fish such as salmon (see related story on page 1).

Now that we’ve fueled up the car, it’s time to look at performance. Whether you’re a jalopy or a Jaguar, you burn off calories all the time. But the rate (see chart at left) depends on many factors, including your weight, gender, muscle mass and how much you exercise, says exercise physiologist Eric Witzel of Lehigh Valley Hospital and Health Network. Surprisingly, your body does most of its calorie-burning (about 60 percent) at rest. It’s called “basal metabolism.” The work you do digesting food accounts for another 10 percent, and physical activity the remaining 30 percent.

Calories loom large when you’re trying to lose weight, and it all comes down to a simple equation: If you eat more calories than you burn, you gain weight. If you burn more calories than you eat, you lose weight. To maintain your present weight, keep the two numbers equal.

“Women need to consume about 12 calories for every pound they weigh and men 14 to 15 calories per pound to maintain weight,” Bentler says. For example, a 180-pound man who wants to stay there needs 2,520 to 2,700 calories daily.

To lose a pound a week (a safe rate of weight loss), you’ll need to trim 500 calories a day. You can either consume less or exercise more. The best strategy, say Bentler and Witzel, is to do both.

Calorie Makeover

Alice wants to lose 20 pounds and become more physically fit. Dietitian Mildred Bentler revamped her diet (see below). Between that and a new exercise program, Alice will trim 500 calories daily—enough for a healthy weight loss of one pound a week.

Alice’s BEFORE Menu	Alice’s AFTER Menu
Breakfast 5-oz. bagel with cream cheese Coffee with cream and sugar	Breakfast Whole-grain English muffin with peanut butter Orange
Lunch 6-inch Italian sandwich with cheese Coffee with milk and sugar Large chocolate chip cookie Diet soda	Lunch Mediterranean chicken salad Diet soda
Snack Granola bar Coffee with cream and sugar	Snack 8-oz. lowfat yogurt Coffee with lowfat milk and sugar
Dinner 1 1/2 cup spaghetti with meatballs 3/4 cup tomato sauce Salad with creamy Italian dressing 2 slices garlic bread Diet soda	Dinner 1 cup spaghetti with grilled shrimp 1/2 cup tomato sauce Salad with olive oil vinaigrette 1 bread stick Diet soda
Snack 1 cup ice cream	Snack 1 fudge popsicle
TOTAL: Calories: 2,600 Carbohydrate: 48% Protein: 13% Fat: 38%	TOTAL: Calories: 2,380 Carbohydrate: 59% Protein: 19% Fat: 22%

How Many Calories Are You Burning?

Your Weight

Activity per half-hour (unless otherwise noted)	100 lbs.	150 lbs.	200 lbs.
Bicycling, 13 mph	200	300	400
Gardening, moderate	90	135	180
Golfing (with cart)	70	105	140
Walking, 4 mph	100	150	200
Hiking, no load	155	232	310
Running, 8 mph	305	458	610
Vacuuming	75	112	150
Washing the car	75	112	150
Weight training (90 sec. between sets)	125	188	150

This page last updated 2/12/08 04:08 PM