If you are an average adult, you probably qualify for being a time-pressured person. That is, you most likely have more things to do than you have time to do them. If this is the case, one of the things you may not do that you should do is exercise.

It is an unfortunate fact that 6 out of 10 adults lead totally sedentary lifestyles. Even more problematic, only 1 out of 10 adults performs sufficient physical activity to attain measurable fitness benefits.

Perhaps because it doesn't take time, dieting is the preferred approach to weight loss for many people. Although low calorie diets may produce temporary results, it has proved unsuccessful for permanent bodyweight improvements.

But why do less than 10 percent of dieters keep the weight off? Because keeping fat off is closely related to keeping muscle on. You see, average adults have two problems. One, they are adding about 15 pounds of fat every decade of life. Two, they are losing about 5 pounds of muscle during the same time period. So what the bathroom scale registers as a 10-pound weight gain actually represents a 20-pound change in body composition. If the body were a car, this would be analogous to driving a bigger automobile with a smaller engine.

While it is obvious we need to reduce our fat stores, it is just as necessary to replace our muscle tissue. We need larger engines (muscles) to burn more calories (both awake and asleep), so that we can eat reasonable amounts of food without gaining fat weight.

At this point, you may think that we are going to recommend regular aerobic exercise such as walking, cycling or stepping. You're right. Aerobic exercise is almost as effective as dieting for reducing body fat. In addition, it conditions your cardiovascular system and reduces your risk of heart-related diseases. But it does not replace muscle tissue, and it does take time . . . more on that later.

Our best advice, however, is to do regular strength training to replace muscle tissue and recharge your metabolism. In addition, strong muscles may reduce your risk of osteoporosis , colon-cancer , diabetes , low-back pain , high blood pressure , arthritic pain , and depression.

Perhaps you are convinced that a combined activity program (aerobic exercise and strength training) is a better health and fitness approach than dieting. Indeed it is, but you still may not have enough time for such an active lifestyle. After all, most of your active friends probably spend at least an hour a day on their exercise program.

A research, conducted at the South Shore YMCA, required the participants to train just 20 minutes a day, Mondays, Wednesdays, and Fridays, for a one-hour-per-week exercise commitment.

After only 8 weeks (8 hours) of training the 59 men and women made significant improvements in their body composition and physical fitness. On average, they lost 4 pounds of fat, added 2 pounds of muscle, increased their overall muscle strength by 23 percent and improved their cardiovascular endurance by 12 percent.

The training program consisted of three strength exercises and 15 minutes of aerobic activity. The participants did one set each of leg presses for the front and rear thigh muscles, bench presses for the chest, shoulder and triceps muscles, and compound rows for the back and biceps muscles. Each exercise was performed for 8 to 12 repetitions and required about one minute for completion. The participants also worked their way up to 15 minutes of continuous cycling or stepping to round out the 20-minute training session.

The program participants were very pleased with their body composition changes and physical fitness improvements. In fact, over 90 percent of the participants committed to continue their hour-per-week exercise program, and many have convinced family members and friends to do the same.

Originally, it was believed that brief exercise sessions would be better than no physical activity, and this proved to be a correct assumption. However, the program participants did much better than was anticipated, indicating that 20-minute exercise sessions may be highly effective for enhancing body composition and physical fitness.

Don't let the tyranny of time prevent you from enjoying the benefits of a simple, short, and successful exercise program. Consult with a personal trainer or fitness instructor in your area to design a basic but brief exercise program that will enable you to establish a physically-active lifestyle.