With Visaria here, 15% sounds about right. bodybuilders @10 to 11%BF look very vascular and carry a full 6packs. It s bit depressing once u than evaluate ur own body fat but that seems to be the sad reality(as far as dexa scans are concerned).
That s why the 15 to 20% average body fat sounds low if u talk about the male adult population. Not sure how this number was calculated
Only 21% chance that he is NOT natural according to my trainer whom has developed some sort of algo which looks at the FFMI (fat free mass index). Compare that to Frank Zane which comes in at 86% chance that he is NOT natural.
It is not only a matter of general size. It's also the look. Even at ~similar overall body compositions, a steroid user will look different from a lifelong natural.
https://www.cdc.gov/nchs/data/nhsr/nhsr122-508.pdf You can calculate an estimate for bf % if you have the BMI number.