I'm saying I am v.v. suspicious of the "childhood trauma made us abnormal and w/o trauma we'd all be thinner than we are" paradigm.

And I am also simultaneously questioning the notion of a "normal" body, yes. (and, cough, "designed"? Optimally or otherwise.) There might be a range of weights (NOT BODY FAT) that our bodies are optimized to carry, if you see the distinction, but that doesn't make it a normal body. It makes it an optimized one.