Body Mass Index is a bad measurement
When you tell people that being thin to the point of being unhealthy is desirable, then people are going to write you off and ignore what you say.
We keep hearing that obesity is a national health crisis and when you walk around the streets of any city you can see that this is a problem. One author at The Federalist is calling on the federal government to "do something" about it.
First, no. The federal government has absolutely no constitutional authority to "do something" about obesity. If government is to do anything to help or encourage people to lose weight, it should be state or local government. The Tenth Amendment does not cease to exist just because a Republican wins an election.
However, the question remains: How do we define obesity? I am 5'9" and 185 pounds. In order to get to my ideal weight according to body mass index, I would have to lose 30 to 35 pounds. That is insane. I would be emaciated. I could probably stand to lose 10 or 15 pounds, but losing 30 would be unhealthy.
We are facing the same problem with obesity that we faced with COVID-19 four years ago. The so-called "experts" are so extreme that people dismiss what they have to say out of hand, and then the good, scientifically sound advice is tossed aside with the foolishness. When you tell people to wear a mask during sex, you lose credibility when you tell people to wear a mask in a public place.
When you tell people that being thin to the point of being unhealthy is desirable, then people are going to write you off and ignore what you say. It gives the "fat acceptance" movement more credibility, which is unfortunate. Carrying too much weight increases the risk of stroke, heart disease, diabetes and more. We should not bully people because of their weight, but we should not lie to people and encourage them to be unhealthy.
Body mass index is an absolute joke. It ignores lean muscle mass for a context-free number. A large number of athletes, especially those who engage in weight training, would be considered "overweight" under the BMI rubric. We should not be relying on BMI as a measure of obesity or being overweight.