For decades, health experts have relied on body mass index (BMI), a ratio of weight to height, to classify people as underweight, normal weight, overweight or obese. But sometimes, you need more than two numbers to understand your health. For example, BMI can't tell you how much of your weight is fat versus muscle. That's why a growing number of researchers and physicians prefer other metrics instead. NPR health correspondent Allison Aubrey breaks down the history and shortcomings of BMI, and shares other methods to get a fuller picture of your body. Learn more about sponsor message choices: podcastchoices.com/adchoices NPR Privacy Policy