Exercise Combats Age-related Weight Gain

With age, Americans tend to gain weight and become increasingly overweight. One prescription has been to encourage all Americans to get more exercise in their daily lives. But how much exercise is enough to prevent weight gain later in life?

Dr. Larry T. Wier and other researchers tested 34 male and 155 female employees at the NASA/Johnson Space Center in Houston over 5 years (Int J Obesity 2001; 25:613). After completing a 3-month education program in the employee health-related fitness program, employees participated in the self-supervised exercise program that included periodic re-testing.

Fitness tests were offered on a voluntary basis every 3 months. The periodic evaluations included measurements of weight and percentage body fat; the researchers also recorded each participant’s results on 1-minute bent-knee sit-ups, 1-minute pushups, and a sit and reach test of low back/hamstring flexibility.

Weight was measured at baseline and follow-up, and the amount of habitual physical activity was derived from the multiple rating of the NASA Activity Scale, or NAS. The 11-point scale (0-10) is based on the total minutes spent per week in exercise or the total weekly miles run or walked. Subjects used this scale to rate their general activity over the past 30 days. A rating of 0-1 would indicate very low activity, while a rating of 2-3 would represent regular recreation or slight work in such activities as golf or yard work for a weekly total of between 3 minutes to 2 hours. Ratings of 4-10 represented regular participation in aerobic exercise and from light to heavy exercise.

Substantial but manageable regular exercise is best

The researchers found that a substantial but manageable amount of regular exercise was needed to avoid weight gain. In this case, the activity needed to maintain weight for 5 years required a mean NAS score of 6.0 for men and 5.6 for women. This meant participation in aerobic exercise and light-to-heavy exercise. Weight change was a function of several factors, including initial weight, time between tests, gender, and physical activity habits. For the same level of activity, heavier men and women had the most favorable change in body weight.

Age and gender made a difference. Older men gained less weight than younger men for the same baseline weight and level of physical activity. This age-related difference was not noted among women. The level of physical activity had a greater effect on weight change for higher baseline weight levels. For men, the influence of exercise increased from the age they started a regular exercise program, so that if two 100-kg men exercised at an average NAS level of 6 (active), a 25-year old man could expect to lose about 0.15 kg per year, while a man 30 years older would lose nearly 0.6 kg per year. In contrast, a 90-kg woman with a mean NAS of 6 would lose about 0.7 kg per year while a 70-kg woman with the same NAS score would lose 0.2 kg per year. At the end of the study, the authors found that men maintained a higher mean activity level than women and thus had an insignificant amount of weight gain (over 5.7 years). Women exercised less and had a mean weight gain of 1.4 kg over 4.9 years. Only men and women who maintained a high level of exercise (NAS >6.5) lost weight.

Self-reported activity records, such as those using the NAS, can be helpful for predicting long-term weight change and may be useful when counseling clients about the value of physical activity for weight control.