Diet Versus Exercise.

Which is better when you want to lose weight?

To stay slim and trim, John runs five miles almost every day.

Because of his vigorous workouts, he feels he's earned the right to eat whatever he wants. His wife, Sue, however, would rather read the fine print on the insurance policy than get anywhere near a treadmill or gym. Her solution to weight control is carefully selecting what she eats. That's why you're more likely to see her reach for a piece of fruit instead of a cookie or slice of cake.

So which one has the more effective approach to staying slim? Well, a lot depends on whether your weight goal is short- or long-term. If your objective is to reduce body fat and keep your weight at a healthy, comfortable level, research has confirmed that regular exercise is the most important factor for long-term success.

You can lose weight without exercising. People do it all the time. "[But] the ones who manage to keep off lost weight for at least a year are involved in a regular exercise program," says nutritionist Bonnie Freedman. "[By comparison], a substantial number of people who lose weight through diet alone gain it back after a year."

There are several factors as to why. For many people, dieting for an extended period of time is just too difficult. It's like treading water--you can do it for a while, but pretty soon you're going to sink. In dieter's terms, that usually means ending up frustrated, unhappy, and even more inclined to overindulge.

"Also, exercise is a very effective and lasting way to shed pounds because it changes the energy equilibrium in your body--your metabolism--by increasing the amount of energy you expend in an average day," Freedman says. Exercise helps your body burn calories more quickly. "And people who exercise on a regular basis tend to be more physically active throughout the remainder of the day, adding to their calorie expenditure," Freedman adds.

Most important, exercise increases muscle mass by increasing the size of muscle fibers. Calories from fat stores are needed and burned to maintain these fibers. In other words, the more muscle you add, the higher your metabolism rate will be.

Even so, if you're looking to shed some weight, you'll have to be patient if you're going to do it by exercise alone. A pound of body fat contains about 3,500 calories. In order to lose a pound you'll have to cut 3,500 calories from your diet, or burn 3,500 extra calories through exercise.

If you're truly interested in losing the weight, you should consider combining exercise with a program of caloric restriction, since you may be surprised by the modest numbers of calories you actually burn in the exercise you do. Although there are many other benefits to exercising, such as clearing your head and relieving stress, it does require a lot of time for the relatively small reduction of daily calories.

For example, a typical breakfast muffin could contain about 500 calories. "Burning off 500 calories could take a couple hours on a stationary bike. That's a lot of effort for a five-minute indulgence," says John Joyce, fitness director at Bally Total Fitness.

So where do you begin? As an incentive, many people use an upcoming event, such as a wedding, holiday, or family reunion, to reach their ideal weights. That's fine as long as you are realistic and allow yourself plenty of time before the occasion.

"The general `rule of thumb' should be to lose about half a pound a week. This slow-and-steady plan will keep you from cutting back too dramatically on your food intake. Not eating enough will not only cause you to be hungry and grouchy all the time, but will actually lower your metabolism," Joyce says.

A great way to trim some calories from your diet is to add more vegetables and fruits to your meals because they're low in calories but full of water and fiber. So you'll feel full without taking in the extra calories.

The same holds true for snacks. Instead of eating a 200-calorie bag of chips or a candy bar in the middle of the afternoon and then needing a 45-minute walk to burn it off, how about an 80-calorie apple followed by that walk? Now we burned an extra 120 calories instead of breaking even. Plus, the apple actually contains some nutritional value.

With the sophistication of today's workout equipment, it's fun and motivating to watch exactly how many calories you're burning right down to the minute. But don't let all the excitement these electronic gadgets provide encourage you to attempt more than your body is currently capable of safely enduring. If you're a beginner, you'll last about 30 seconds if you crank up the machine to its max. And you'll likely burn out or risk injury.

There's a better approach to calorie burning. First, choose something you enjoy doing yourself, or with a family member or a friend. You don't want to dread the activity after just a few workouts. Also, choose an activity that you can sustain for a while--say, 20 to 30 minutes. For example, running will burn more calories than walking. But if running wipes you out after the first block or is hard on your knees or ankles, you're better off with the lower-impact approach of power walking.

After the first few weeks you'll be amazed at how much better you'll feel during and after each workout. But after several months of basically doing the same thing, you may plateau and not make much additional progress with your same workout. If you don't have the time to increase your workout routine slightly, you may opt to conservatively increase the weight and/or repetitions in your strength-training program.

Just when everything is going right and the results are starting to pay dividends, you might be plagued by an unfortunate injury. It may not be anything more serious than a twisted ankle, but it could be enough to sideline you from any weight-bearing exercise for a while.

Does this mean you're going to blow everything you've worked so hard to achieve? Well, not necessarily. But you will have to make some adjustments, especially if you've relied strictly on exercise to lose weight. The days of a vigorous workout followed by the reward of whatever you want to consume are over--at least until you get back on your feet.

To keep the pounds off while you're nursing yourself back to full strength, make sure you eat a healthy low-fat diet and stay away from calorie-rich snacks and sweets.

If it's a foot injury, you can still remain healthy, lean, and toned. You might not be able to do aerobic exercises right now, but you can work out with abdominal exercises and seated weight training. You may also look for videotaped workouts that offer floor work and stretching moves on a mat. For more serious injuries, a doctor or physical therapist may be able to provide exercises that are suited specifically for your needs.

Losing weight doesn't have to be grueling. You just need patience to work off the pounds and inches at a realistic, healthy pace. Remember, you didn't pack it on overnight, so you might not take it all off right away, either.

And if you get your spouse and children involved in eating right, and exercising on a regular basis, your new healthy lifestyle can improve the way your whole family looks and feels--a change you all can enjoy.

Conrad Theodore writes on health topics from Lake Forest, Illinois.