how can i tell the difference?
If you have to ask, it's probably fat.
Have you dropped about 100lbs?
fat is well FAT full bellies of tissue. like "pinch and inch" where as lose skin would hang saggy you can push it together and it looks like a pug dog or an english bull pugs face. Hnags like a udder. you can grab it and pinch it together its not full. its loose excess skin. speaking from expeience here.
there is a AWEFUL pic in Chris's latest article of loose skin.