For those who read the New York Times's stories denigrating BMI as an obesity metric, you have heard only a small part of the story. Their latest senasationalist coverage says that 18% of BMI-obese people are not really obese, with 12% labeled as "healthy obese" and 6% called "skinny fat".
The first question to ask when faced with those numbers is how is "true" obesity defined? A claim that 18% of BMI-obese people are misclassified is a claim by someone that they know the true state of "obesity". But how is obesity defined? You know what, there is no objective measure. BMI is based on height and weight. Other measures are based on waist size, body fat, and so on.
Those numbers make an assumption that body-fat percentage as measured by the DXA method is God's word on obesity. Someone is making a claim that the 12 percent of people who are obese under BMI but not obese under DXA is "healthy". The claim is not even that these people are "not obese"--they are "healthy". This isn't science.
Further, DXA requires a body scan on an expensive machine while BMI is a measure that can be computed and monitored by anyone at home. That alone makes using DXA as a measure impractical.
Further, there is a huge literature that establishes the correlation between BMI and a variety of health problems. There is very little research that shows DXA as correlated with health problems. (Much of this is because DXA is not readily measured.)
Further, the chart is a bit misleading because officially, BMI-obese is BMI over 30. Between 25 and 30 is called "overweight". Almost all of the "misclassifications" are BMI-overweight so those "healthy obese" are just under the BMI-obese definition. In any case, the worst that could happen to these 12% is that they are asked to exercise, eat healthy, etc. What is the cost of such misclassification? The "skinny fat" group is a bit more concerning but where is the proper scientific evidence proving that this group faces abnormal death risk from fat?
Chapter 2 of Numbersense (link) has the full story on this misguided argument about DXA vs BMI. The bottom line is: our obesity crisis will not be solved by changing how we measure obesity.