[Domenic_S]

No, it's that some extreme outliers have insane BMRs. It's still a calories-in-calories-out situation, it's just their base calories out is so high without doing anything special it's like a superpower. I've only met a few, but it's a real thing! Most of us go through something similar (but to a lesser extent) in our teen years. A few seem to keep it forever.

[semi-extrinsic]

I'm curious whether anyone can provide some scientific evidence supporting the theory that these people actually burn calories faster? Seems like it should show up very clearly on their core body temperature (thermodynamics and all).

An alternative hypothesis would be that these people have a less efficient digestive system, so more of the calories just pass through.

[Domenic_S]

Here ya go:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4535334/

[semi-extrinsic]

Oh neat, they use oxygen consumption as a proxy for metabolism rate. That's actually really clever.

Still would be interesting to see whether it's correlated with body temperature, or if people with high metabolism naturally shed heat faster.

[jtuente]

Most people were simply far more active in their teen years, whether they realize it or not.