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Comment by karmarepellent | Hacker News Reader

I think BMI is a little confusing when it is applied to some categories of healthy individuals like endurance athletes and others. When I ran (a lot) in my early to mid-twenties my BMI was always "underweight". Yet I have never felt better.

The same probably goes for climbers. Some of the climbers I know are inredibly lean and their BMI is certainly not in the "normal weight" range. Yet they are able to push their bodies to incredible feats.

All that is to say, I suppose BMI stops to be useful at some point while, at the same time, it may be a good instrument to measure your progress during weight loss. It can be both useful and not, depending on who you apply it to.

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BMI is really a tool for helping to give indications of risk factors. If you have a BMI of 15, it's likely you have risks of various diseases. It's not a slam dunk, but a risk. But if you've chatted with a health professional and you're both happy that you're outside of the risk factors, then you'd not need to worry much. Some people are fine at BMI 26 or 17, some are outside of their healthy range at 24 or 19. It's a guide, not a rule.

The people who DO fall outside of the model are not that common though, especially if you're white. And these days the model accounts for more minorities, so even though it has issues, it's still worth listening to as it can highlight potential problems before they actually become problems.

BMI measurements do have some signal for endurance athletes.

People who win running competitions are quite tightly grouped BMI-wise.

And for running I guess that makes sense, a kg of muscle weights as much as a kg of fat. Even if that kg of muscle is a lot healthier than the kg of fat.

Yes I should have clarified: I think the BMI levels (underweight, normal etc.), that is the "wording" cannot necessarily be applied to athletes (edit: and could be misleading for people and their self-concept when their weight is perfectly fine). You are right of course that the top runners in a competition likely stand out BMI-wise from the rest.

I've heard that waist-to-hip ratio is a better measure of overall health because it more directly measures the amount of visceral fat, but that wasn't wasn't what the study being quoted was measuring.

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