How Fast is Your Engine Running?
Jacqueline Stenson - Contributing editor MSNBC

High-tech gadgets offer new ways to measure metabolism

Q: Is there a way to determine how fast or slow your metabolism is?

A: Yes, there are several options for determining what’s known as your resting metabolic rate (RMR), the number of calories your body burns at rest to carry out typical body functions like breathing and pumping blood. RMR makes up most of your metabolism – the total number of calories you burn in a day.

The traditional way to measure RMR is to use a standardized formula that factors in your sex, weight, height and age. One of those formulas is known as the Harris-Benedict equation:

• For women, 655 + (9.6 x weight in kilograms) + (1.8 x height in centimeters) – (4.7 x age in year)
• For men, 66 + (13.7 x weight in kilograms) + (5 x height in centimeters) – (6.8 x age in years)

That’s a lot of number-crunching, and when you’re all done, the results may not be very accurate for you, particularly if you’ve overweight. Formulas like this one are based on average people, and all of us aren’t average.

“Many equations just provide rough and dirty ballpark estimates,” says Cedric Bryant, chief exercise physiologist for the American Council on Exercise in San Diego.

And formulas simply don’t account for the fact that you may pack on pounds faster than someone else, or vice versa. We all k now those lucky few who seem to eat whatever they want and never gain an ounce, while others continually battle the bulge.

“There are just some of us who are blessed with higher metabolisms than others,” Bryant says.

But now there are other options for determining how fast or slow your engine’s running. Tow high-tech gadgets available at many health clubs and weight-loss centers promise to give you a more accurate assessment. Once is called BodyGem and the other is New Leaf. With both, you breathe into a mouthpiece of face mask that determines your body’s exchange of oxygen and carbon dioxide while at rest. The devices then spit out your individualized RMR, which Bryant and other experts say is more accurate than the mathematical formulas.

The RMR figure can then be used, along with estimates of how much energy you burn each day through physical activity and how many calories you ingest, to tailor-make a fitness and diet plan – how much more you need to exercise and how much less you need to eat- to help you achieve your weight-loss and fitness goals.

The New Leaf system goes a step further: It can be worn during an exercise test on a treadmill or stationary bike to determine how many calories you’re burning during exercise and to calculate your target heart rate. It can also be used over time to determine how much your physical fitness is improving.

The technology behind New Leaf stems from sophisticated devices known as metabolic carts that elite athletes have used for years to gauge their performance over time. Endurance athletes, for instance, like to track the point at which they reach their anaerobic threshold-essentially when they stop burning oxygen efficiently, “hit the wall” and simply can’t go any further. Then, the athletes train to push that threshold higher, increasing their overall performance.

A BodyGem assessment costs about $50 while New Leaf can run as much as $200, depending on how much feedback you desire. The companies’ web sites can provide a list of facilities near you that offer the devices. While these products may provide direction and inspiration, you’re stuck with the hard part- exercising and eating right.

“In all successful weight-loss programs the key issues are with lifestyle changes, now really with RMR,” says Len Kravitz, coordinator of exercise science at the University of New Mexico at Albuquerque.