system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do some fat people's stomach look round and firm and some have flappy skin?
gpt
The flappy skin type of belly fat is called subcutaneous fat, and it is beneath the skin, but outside of the abdominal wall muscles. The firmer type of belly fat is caused by visceral fat, which is inside the abdominal wall and around the internal organs. The visceral fat often accounted to be less unattractive, but is much more unhealthy and associated with diabetes and other diseases.