The study found that nearly half of “overweight” people (25 <= BMI < 30) were metabolically healthy, as were 29% of “obese” people (BMI >= 30). But over 30% of “normal weight” people (18.5 <= BMI < 25) were metabolically unhealthy.
Perhaps it is not surprising, since many heavier people are heavy with muscle, while many normal weight people have low muscle and high body fat. Differences in exercise habits and genetics can also mean that different people may have different levels of metabolic health for the same BMI and body fat percentage.
The background is a controversy about whether employers should (or should be allowed to) charge higher premiums for employer sponsored medical insurance based on BMI, which is one of the potentially allowed factors among others (e.g. enrollment in wellness programs, the metabolic health markers looked at in this study, etc.).
So… someone is wasting money trying to prove that a rough guide number should not be used as a precise measure of health? That’s just like using my Fitbit to measure a marathon course… I think you answered your own question right here:
This is exactly the point: there is NO single factor that would tell how “healthy” a person is. It is always a combo.
The BMI is the classic example of something that should be a rough rule of thumb being turned into something that is used as gospel. The BMI is easy to calculate, but like the height/weight tables that predated it, it is based on very broad assumptions that may or may not have any meaning. Doctors love it, because it is a magic number to yell at patients with, insurers love it because it is an easy way to grade people (and the fact that it is inaccurate in terms of health is even better, because they can charge perfectly healthy people a higher rate, while the risk of them having to pay out is less). Many pro athletes are obese under the terms of this, as are people who happen to be muscular, it also doesn’t take into consideration frame size either, a slight person at 6’ 165 might be fit, but someone who has a heavier frame would be underweight at that weight. It has value as a starting point, but as a measure of health, it is far too simplistic, I suspect if this was challenged in court (which it will be, if they start basing medical insurance pays on it), and the ‘science’ behind it was revealed, it would be a loss for those using it. The research doesn’t back BMI, unlike smoking, where the cost of smoking is well documented health wise.
Neither does waist circumference, 5k time, hours of sleep, etc. taken alone. Because it is a “number,” it must be a true measure of something - contrary to this common belief, a single number is not usually a measure of something as complex as one’s health.
BTW, weight and height are not the only parameters that insurance cos ask for and use in calculating risk. The questions usually include smoking history, drug use, etc.
Almost any measure isn’t valid for everyone. For example, if you’re a serious athlete, you may have a very low heart rate. The same heart rate would be a sign of a serious problem for most people.
The press has latched on to this study and misinterpreted the results. Perhaps it’s true that many overweight people are metabolically healthy, but the fact remains (I suspect) that these people would be even healthier if they shed some weight.