A recent Jane Brody article for the NYTimes reminds us that BMI is imperfect and only a crude measure of fatness in individuals. The biggest challenge of BMI standards is their inability to measure fat against lean muscle.

A woman can get back in the gym at 50, transforming her body out of fatty tissue and into weight-exercising muscle and still have the same BMI. Because a pound of fat takes up four times the fat of muscle, her body can change significantly — appearing toned, defined and smaller — but her weight has remained the same.

“The B.M.I. tables are excellent for identifying obesity and body fat in large populations, but they are far less reliable for determining fatness in individuals,” explained Dr. Carl Lavie, a cardiologist at the Ochsner Heart and Vascular Institute in New Orleans. via NYTimes

Degrees of body fat is a better measure of obesity and overall health.