If someone have skinny look but is all flabby underneath, you can call him a skinny fat. When you touch skinny fat, your touching hand sinks into fat before reaching muscle.

如果一个人看起来瘦瘦的，但浑身的肉却软趴趴的，你可以称他为“浑身肥肉的瘦子”。如果你碰到一个“浑身肥肉的瘦子”，你的手碰触到的将是肥肉而不是肌肉。

Skinny fats have a high fat percentage and low muscular mass. They are usually those people who have a low caloric diet, that's why they are skinny, but are not involved in any sports activities or trainings and that's why they don't have any muscle.

“浑身肥肉的瘦子”肥肉多肌肉少。他们通常进食的卡路里数少，所以看起来骨瘦如柴，但因为没有参加体育运动或锻炼，所以没什么肌肉。

Example:

People who don't lift get skinny-fat. They're thin but as weak as kittens.

不练举重的人就会变得浑身肥肉。他们瘦瘦的，但却弱得像小猫。

A: That girl is hot! 

B: Dude, what are you talking bout, that girl is skinny fat!

甲：那个女孩好辣！

乙：老兄，你没看错吧，那个女孩是个浑身肥肉的瘦子！