I think that this means human beings in Developed countries are optimized to be healthy in fat bodies, because their bodies are accustomed to eating a lot.
On the other hand, keeping fit has been a problem among females who want to lose weight extremely, and are actually slim or skinny. Among females, silent competitions for being slim are held elsewhere. But, from my viewpoint,a fat body is more attractive than skinny one.
So, if there is a girl who reads this article, I recommend you to be a little bit fat rather than losing weight.