Can you exercise your way to ideal weight?

Can You Exercise Your Way to Ideal Weight?

Mary was discouraged. Her brow creased, she reviewed the carefully written notes in her exercise and weight logbook. Almost every evening for nearly eight weeks now, she had been walking briskly for 30 minutes before supper. This totaled from 10 to 12 miles a week. Her aim had been to lose the 10 extra pounds that she had slowly gained during the past five years. Yet she still weighed 140 pounds, only one pound less than before she had begun her exercise program. Finding an extra 30 minutes in her schedule had not been easy. What had gone wrong?

I've worked with many "Marys" during the past 15 years. Early in my professional career my response to this question would have been "You probably increased your food intake, negating the effects of your exercise program." Now I know better.

The truth about exercise. Researchers throughout North America, including my team at Loma Linda University, have taken a close look at the relationship between exercise and weight loss. We are proving true what many disappointed exercisers have experienced - exercise alone is a weak weapon in the "battle of the bulge."

In 1985, I organized an intensive five-week research project involving 21 physically inactive women who weighed 30 to 40 pounds more than they should. All subjects were placed on a 1,268-calorie lactovegetarian reducing diet, with all meals weighed and served in our research kitchen at the School of Public Health. After random selection, half the women remained physically inactive while the other half were placed on a brisk walking program consisting of five 45-minute sessions per week at a heart rate of 135 beats per minute. Although the exercising women were very faithful to their exercise program, averaging 15 miles per week, or 75 miles for the entire study, they lost exactly the same amount of weight - 12 pounds - as did the inactive group. In other words, all the weight loss occurred because of the reducing diet, not the exercise program.

At first we were quite surprised by our results. Our methods had been rigorous, and subjects in both groups had complied strictly with all the research project requirements. We dug into the research literature and quickly determined that many other researchers using similar methods had also reported that exercise added little or nothing to the weight loss effects of a reducing diet.

For example, Dr. Phinney of the University of Vermont College of Medicine put 12 overweight women on a 720-calorie reducing diet for four weeks. Half the group exercised for one hour a day while the other half remained physically inactive. Subjects in both groups lost an average of 15 pounds, with exercise adding nothing to the total pounds or the amount of body fat lost.

Dr. Hagan of the Aerobic Research Institute in Dallas, Texas, placed 96 men and women into four groups - a control group, an exercise-only group, a diet-only group, and a diet and exercise group. Subjects in the exercise groups walked and jogged for 30 minutes, five days a week. Dieters were placed on a 1,200-calorie diet. The subjects in the exercise-only group did not lose any weight during the 12-week study, while diet-only subjects lost about 15 pounds. Subjects who exercised and dieted lost only a few pounds more than the diet-only group.

The Loma Linda University research team recently organized a study to determine whether or not a brisk walking program could have any effect on weight loss when participants were allowed to eat as they desired in their homes. Researchers had found that exercise added to a reducing diet had little effect on weight loss. Maybe in a "free-living" situation, where subjects ate normally in their homes, regular exercise would cause some type of change in appetite desire, leading to weight loss.

We chose 36 overweight, physically inactive women, and randomly divided them into brisk-walking and sedentary groups. For 15 weeks, the exercise group walked three miles a day, five days per week - a total of 225 miles for the entire study. Women in both groups were told to "eat as you desire," while my research team monitored their food intake through diet records. The exercise group started the study at 167 pounds and 36 percent body fat - and ended the study at exactly the same weight and body fat percentage, while the inactive group gained 3.5 pounds. After a careful analysis of the data, we concluded that when a group of overweight women are told to "eat as you desire," brisk walking may help to prevent a few pounds of weight gain. But for any meaningful weight loss to occur, a reducing diet is necessary.

Reasons that exercise is not a major weapon. When you look at the actual number of calories burned during exercise, you can quickly realize that the human body can accomplish much while expending relatively few calories. Let me explain.

Let's say that today you go for a three-mile brisk walk between 5:30 and 6:15 p.m. During that 45-minute period, you will expend a total of 215 calories (if you weigh 150 to 160 pounds). What you may not realize is that if you decide not to go for a walk during that same period but sit completely still, you will still expend 50 calories to keep alive. If you moved about engaging in a few household chores, then 25 to 50 more calories will be expended. In other words, the net difference is quite small, only about 115 to 140 calories. One pound of human fat contains about 3,500 calories. Do you get the picture? It's going to take more than one month of walking 15 miles a week to lose just one pound of fat.

We have also detected that some exercise research subjects "rewarded" themselves during the rest of the day by either resting or eating more than usual. This further diminished the effects of the exercise.

Well, you say, how about if I run instead of walk, or exercise for a longer period of time? Fine - this will definitely add to the total caloric expenditure, and become important for weight control, especially for the athlete. However, we have found that some overweight subjects are barely able to tolerate three miles of brisk walking per day without developing pain in their feet and knees. Several of our subjects had to use a stationary bicycle for several days until they were able to continue their walking programs. So although normal-weight individuals may be able to tolerate harder or longer exercise bouts, making exercise more meaningful in terms of weight management, most overweight subjects can't do this because of the stress this brings to their feet and legs (see box). In addition, setting aside more than 45 minutes for exercise each day is more than most people's schedules can handle.

The benefits of exercise for the overweight. Despite all this, I still counsel all my overweight clients to exercise. And here's why. Although control of diet is the real power behind losing weight, regular exercise is meaningful because it leads to many important improvements in health and fitness.

One of the strongest benefits is the effect of exercise on psychological health. We have found that brisk walking leads to dramatic improvements in mood and general well-being, while reducing feelings of anxiety. In addition, heart and lung fitness and blood-fat profiles are improved, while risk of disease related to being overweight is lowered.

So I would counsel Mary to keep on with her exercise program because she will feel better and improve her health. However, to lose those 10 extra pounds, changes in the quality of her diet will need to be made. In particular, research is showing that a reduction in the fat content of the diet holds the greatest promise of a meaningful reduction in body fat (see chart). For example, if just 4 tablespoons of oil are removed from the diet each day, about one pound of fat can be lost from the body each week, if all else stays the same.