Ask the Coach: Measuring Fat
Heading out the door? Read this article on the new Outside+ app available now on iOS devices for members! Download the app.
Monitoring body composition for health and training
My husband and I are looking into a body-composition scale to monitor fat percent and body-mass index (BMI). What are the benefits and drawbacks of using these scales to track overall health and response to training and nutrition programs?
—Sunni Heikes-Knapton, Ennis, MT
As an old software test engineer, I like to tell coaching clients the more data, the better. If you are trying to lose body fat in an effort to get faster, then track your progress with real data. We won’t get into all the issues with BMI, but it’s scientifically nonsensical. Squaring a person’s height doesn’t give you any usable relevant data. Pro-basketball star Kobe Bryant is officially overweight by his BMI, for example.
Tracking body-fat percentage can be useful—too much means less efficient running. But this measurement, too, is not perfect. It is one factor, and has little bearing on how fit your engine is—just how heavy the chassis is.
And determining body fat is fraught with issues. Says Dallas Hartwig, a physical therapist and author of It Starts with Food, “Body-fat scales are simply not an accurate tool to assess your overall health status and training progress.”
However, using a body-fat scale can at least show you how you are trending, i.e. whether you are gaining or losing body fat. If you are fit and have 10-percent body fat, you will run faster than if you are fit with 20-percent body fat.
But, remember, a sinewy runner can still lack aerobic fitness. The key is lowering body fat without losing muscle mass. It means that you are essentially carrying around less weight with the same muscular strength and aerobic engine—which means you will “feel lighter” and move faster.
This article originally appeared in our June 2014 issue. Want more? Subscribe to Trail Runner.