For individuals who exercise, working out within the target heart rate range can be the key to shedding unwanted pounds.

"Heart rate monitoring is a way to quantify the intensity of exercise," said Dr. Jane Corboy, a family physician specializing in sports medicine at Baylor College of Medicine in Houston. "Recent research shows that a high-intensity exercise results in a greater increase in metabolic rate, which results in greater weight loss."

The term "heart rate monitoring" can refer to the broad concept of tracking your heart rate during exercise or the more specific practice of using an electronic monitor.

To calculate the predicted maximum heart rate, the average adult should subtract his or her age grom 220. The target heart rate is 70-80 percent of that number. During the activity, stop and count a pulse for six second; then multiply by 10 to calculate the exercise heart rate.

If the appropriate "zone" seems out of reach, try activities that involve repetitive use of large muscle groups. Walking, running, step aerobics, cross-country skiing, swimming, and cycling tend to generate the most aerobic-training benefits.

Corboy cautions, however, that heart rate can also serve as a warning sign. A rise in resting heart rate, for example, can be a symptom of over-training.