BMI has several cons. Because it can’t distinguish between lean and fat mass, it’s limited. It also doesn’t take age, sex at birth, and ethnicity into account. Here are details about how BMI is limited and some better ways to track your health and weight.

1. BMI doesn’t tell you where body fat is stored on your frame.

Carrying more weight around your middle—specifically visceral or belly fat—is a much more important predictor of obesity-related diseases such as type 2 diabetes, heart disease, and certain cancers, as well as overall mortality than total body fat levels. And BMI alone doesn’t use enough information to help you evaluate all those risk factors.  

2. BMI may not be an accurate health measure for certain ethnic and racial groups.

Crazy fact: The original calculations for BMI were developed nearly 200 years ago by a Flemish statistician. They were then updated in the early 1970s using data from only white European men. As a result, its ranges don’t apply fairly to other ethnic groups and people of color.

For example, research has shown that BMI isn’t a good measurement of health among people of Asian heritage because this group may have an increased risk for metabolic diseases before their height and weight calculation qualifies them as overweight. In the past, BMI has missed health problems among Asians.

That’s why organizations like the American Heart Association recommend that doctors use a different BMI scale for Asians that has lower healthy weight cutoff points. Studies have also shown that BMI is flawed in assessing health risks among Black Americans and people of African descent.  

3. BMI doesn’t consider your sex.

Women tend to have higher amounts of total body fat than men with equivalent BMIs. (We are referring to sex at birth.) Men also have more muscle, on average, than women. Yet, BMI calculations hold men and women to the same weight range standards. It’s also not a great gauge for pregnant and nursing women, who carry more weight and body fat to help nourish their babies. This has been shown not to pose any long-term health risks, despite their higher BMIs.

4. BMI can be particularly flawed among athletes.

One of the most famous examples of how BMI doesn’t work for athletes is Arnold Schwarzenegger. When the former California governor was in the prime of his bodybuilding career, he was 6’0” and weighed around 235 pounds—most of which was muscle, of course. His stats gave him a BMI of 31, putting him in the obese range. What’s more: A study of NFL players found that 60 percent of them would technically be considered overweight or obese according to the BMI chart. That doesn't seem quite right with all that training and weight lifting, does it? And that’s exactly the problem: BMI can’t measure overall body composition—meaning how much body fat you have versus lean muscle mass. Muscle is more dense and heavy than body fat, so it’s possible to fall into the “unhealthy” range even though that’s likely not the case.

5. BMI can underestimate body fat in older adults. 

Ever heard the term “skinny fat”? It describes those who are technically at a normal weight—or maybe even underweight—but have a high percentage of body fat that could pose a health risk. And BMI overlooks this. How does this impact older people? Because as you age, your body naturally loses muscle mass. (Well, without regular exercise, like strength training, to help you maintain it, that is.) This could give you a higher ratio of body fat to muscle—the official term is sarcopenic obesity, or ”skinny fat.” It can definitely occur in younger people, too, but it’s most common among elderly adults.

6. BMI can contribute to stigmas around weight.

There is already a lot of guilt and shame wrapped around the topic of weight. And when someone who is overweight or with obesity goes to the doctor, BMI tends to be the focal point of discussion. As a result, other health concerns could get pushed aside. Or that shame may keep people from seeking the preventative care they need, period. This can lead to higher rates of chronic conditions down the road.