Muscle Mass Beats BMI as Longevity Predictor

This is Scientific American 60-Second Science. I'm Christopher Intagliata. Got a minute?
Doctors routinely measure a patient's body mass index, or BMI.
And if that weight-to-height ratio points to obesity, the doc might prescribe exercise, to shed the extra pounds.
But when it comes to longevity, a focus on weight loss may be misplaced.
Because BMI isn't actually a very reliable indicator of life span.
A more useful measure, some physicians say, might be muscle mass.
Researchers analyzed BMI and muscle mass data from more than 3,600 seniors in a long-term study.
And they tracked which seniors had died, a decade later.
Turns out BMI wasn't much good at predicting chance of death.
But muscle mass was: more muscle meant better odds of survival.
The study appears in The American Journal of Medicine.
There's no cause-and-effect here, just correlation for now.
But study author Preethi Srikanthan, of U.C.L.A., has this recommendation:
"Get up and start moving.
Focus on trying to maintain the maximum amount of resistance training that you can,
and stop worrying so much about dropping calories."
Which could take a little weight off your mind, too.
Thanks for the minute, for Scientific American 60-Second Science. I'm Christopher Intagliata.