An example of what the type of thing intended (I presume) by the previous poster: Fatty-liver disease. "NAFLD is observed in up to 80% of obese people... and in up to 20% of normal weight people". https://en.wikipedia.org/wiki/Fatty_liver_disease

AFAIU, some populations are more likely to exhibit non-overweight, non-obese NAFLD. Likewise for type 2 diabetes.

Er, what? Pretty sure GP was referring to the difference between subcutaneous and visceral fat. Visceral fat is behind the abdominal wall and puts extra pressure on internal organs.