How Well Can a Treadmill Count?

figuring out how many calories you burn remains harder than it appears.

by patrick egan

you want to lose weight. you understand the basic principle: burn more energy, measured in calories, than you take in. it's math, pure and simple. the consumption numbers are easy to find-on food packaging, in nutrition books, even on some menus. nailing down the calories you burn, though, is a more elusive task.

fitness-equipment manufacturers understand your desires. they add tools to their gear that they say will help you reach your goals. but just because those calorie numbers are digital, bright red and flashing doesn't mean you should trust them. some experts question whether tracking calories burned is even worthwhile.

the value of a calorie counter can be described much like a workout: the more you put in, the better it'll be. "the machines that ask for height, age, weight, gender, the more data points it will have, the truer readout of calories you'll get," says gregory florez, a spokesman for the nonprofit american college of exercise and the chief executive of fitadvisor.com.

but he estimates that even the best machines are likely to be 5 to 10 percent off for the average user. "it's a hard, dodgy number to pin down," says florez. that's because exercise equipment can't read a person's lung capacity or tell how much a person sweats or know what kind of fitness level he or she brings to the machine.

some companies say their machines get close to accurate numbers. life fitness treadmills, cross-trainers and bicycles can be found in gyms and health clubs across the world. bob quast, vice president of branding, says the company has a team of scientists in a lab to build and calibrate the calorie counters on life fitness machines. with each new product, or significant overhaul of current equipment, the company will test 50 to 100 people of varying ages, heights, weights and fitness levels using v02 max. that's a cool name for a system that measures the maximal volume of oxygen a person can use when exercising at peak levels.

with all that information, life fitness programs its machines with proprietary algorithms. "it's a little bit of a secret sauce," says quast. when a person steps on one of their machines and punches in personal information, the secret sauce spits out a calorie number.

sometimes there doesn't appear to be much science to keep secret. tony little's gazelle is a fitness product widely advertised on television. the top model comes with a calorie counter and heart rate monitor. a customer-service representative directed inquiries about the device to the manufacturer, fitnessquest.

at fitnessquest, customer-service supervisor chris hackney said the gazelle's counter was calibrated for a 150-pound person. she said that more than one 150-pound person-without specifying how many more-used the gazelle at an outside lab. those tests created the readout numbers that gazelle users see. someone who is not 150 pounds has to adjust the calorie readout-more calories for heavier people, fewer for lighter. the owner's manual doesn't mention this adjustment or how to make it.

"consumers really need to be careful about products they see on infomercials," says henry williford, a professor of exercise science at auburn university, in montgomery, ala. he chairs the consumer information committee for the american college of sports medicine. "if it's a piece of equipment where you don't sweat or do a lot of work, you're probably not getting benefit."

that's pretty close to the message some personal trainers are trying to communicate to their clients. ideally, these trainers would like clients to worry less about specific numbers and focus on more simple things. "you're not doing enough and you're eating too much food," says roy taylor, a nationally certified personal trainer in tampa, fla., describing the plight of most overweight people. the calorie counters, he says, "can be useful. but most people are barking up the wrong tree." the right tree, he said, is simply exercising hard, at least four or five times a week, so that a body feels it.

"most beginners need the distraction" of a calorie counter, says david cascia, who owns elite training and fitness in brooklyn. "it engages them in the machine." but cascia sees problems, too. "people get so in their heads about how much they burn." he says they then go out and eat what they think they burned. cascia says that when people get in shape, they tend to eat better as a result. regular exercisers are more attuned to what's going into their bodies.

"calories are somewhat of an inexact science. they don't give you any indication of the quality of those calories," says kristie salzar, a nutritionist. when she started in her profession 25 years ago, most nutritionists focused on the amount of calories their clients consumed, and salzar simply didn't see results. she's telling her clients to move more-whether it's exercise or simply doing physical activities-and getting them to use intuition. "we're all born to know when we're hungry and when we're not," she says, pointing to a baby's crying as the simplest sign. but adults, she says, eat for many reasons, often psychological, that don't have anything to do with being hungry.

kari viste works out at the downtown brooklyn ymca. while she doesn't consider herself a "calorie counter," she pays enough attention to know how many calories she burns on the elliptical machine. identical 40-minute workouts allegedly burn 420 calories on the newer life fitness model but only 350 calories on the older machine. she hopes the newer model is more accurate.

"i don't think they're very reliable," says viste of calorie counters. so why pay attention? she says it's "more of a game" that helps her reach her goals. but she doesn't use the number to rationalize what she should or should not eat. "i eat pizza no matter what."