Doc: Do exercise machines include ‘basal metabolism’?

Keith Roach
To Your Health

Dear Dr. Roach: When we exercise on a stationary bike, treadmill, etc., many of the machines show the number of calories burned in our workout. Are the calories shown gross or net? For example, if the machine indicates 280 calories after an hour, is that in addition to the approximately 80-120 calories (my guess) the body uses every hour for us to live, or is the 280 calories include the 80-120 calories? We may be deceiving ourselves about our workout and how much we can eat if it is the latter. I’ve asked many people who exercise, as well as those who work at health clubs, and no one seem to know.

V.F.

Dear V.F.: I believe that in most cases the number is intended to show the net calories, the ones expended in exercise over and above the amount of calories we expend on basal metabolism (which is closer to 50 calories an hour for most people). However, the machines provide only a rough estimate, with a potential for error that is pretty large. To measure accurately, the machine needs to know your body weight and heart rate, and ideally should know your VO2, a measurement of how much oxygen you consume at your peak exercise. This is obtainable by a stress test with gas exchange, something few people (but many elite athletes) have done. Some newer machines at the gym allow users to enter in this information, and some smart watches will then give you “active calories” and “total calories.”

I think many of us deceive ourselves in all kinds of ways about exercise and diet. We overestimate our exercise, and I still see people who feel that some calories consumed don’t “count.” But the fact remains that a 2-mile run burns less calories than are contained in many energy bars.

If you are exercising more in order to maintain weight, the best measurement is your weight. If it’s higher than you want, you need to eat less, exercise more or do both.

Email questions to ToYourGoodHealth@med.cornell.edu.