Raleigh, N.C. — With healthy eating and regular exercise at a WakeMed fitness center, Judy Garrett has lost 120 pounds in two years. However, she has learned not to trust the calorie counters on the fitness machines.

“This [machine] says that you burn 25 percent more calories than that one does, so I know that’s not correct,” Garrett said.

The machines track people’s workout times, their speed and heart rate. But can they really count calories burned?

“Well, unfortunately, they really should be used more as a general guideline,” said WakeMed Fitness Specialist Marie Bagin.

Heavily used machines easily fall out of calibration, Bagin said. There are other factors, such as body weight. Most newer machines ask people to enter their weight, but many people don’t.

“If you don’t put in a weight, most machines assume that you’re a 154 pound male,” Bagin said.

Machines with moving handle bars may assume that people are using them when it counts calories.

“So if my arms are not moving, I’m not burning as many calories as I normally would have been,” Bagin said.

Experts say the important point is to count the number of minutes people exercise on a weekly basis. Garrett’s goal is about an hour on workout machines at least five days a week.

“Some days I don’t want to come. I make myself come, and when I leave, I feel so much better,” she said.

The American College of Sports Medicine recommends that adults should engage in moderate intensity exercise, such as brisk walking, for at least 30 minutes, five or more days per week.

People should talk to their doctors before starting any new exercise program.