Diet or exercise: Does one matter more?

Both are important. Diet has a stronger effect on weight loss than physical activity does; physical activity, including exercise, has a stronger effect in preventing weight regain after weight loss.

Weight loss through diet without physical activity, especially in older people, can increase frailty because of age-related losses in bone density and muscle mass. Adding aerobic and resistance training to a weight-loss program helps counter the loss of bone and muscle.

For most healthy adults, the U.S. Department of Health and Human Services recommends these exercise guidelines:

• Aerobic activity. Get at least 150 minutes of moderate aerobic activity or 75 minutes of vigorous aerobic activity a week, or a combination of moderate and vigorous activity. The guidelines suggest that you spread out this exercise during the course of a week. Greater amounts of exercise will provide even greater health benefit. But even small amounts of physical activity are helpful. Being active for short periods of time throughout the day can add up to provide health benefit.
• Strength training. Do strength training exercises for all major muscle groups at least two times a week. Aim to do a single set of each exercise, using a weight or resistance level heavy enough to tire your muscles after about 12 to 15 repetitions.

Moderate aerobic exercise includes activities such as brisk walking, swimming and mowing the lawn. Vigorous aerobic exercise includes activities such as running and aerobic dancing. Strength training can include use of weight machines, your own body weight, resistance tubing or activities such as rock climbing.

As a general goal, aim for at least 30 minutes of physical activity every day. If you want to lose weight, maintain weight loss or meet specific fitness goals, you may need to exercise more.