last time my pendidikan jasmani teacher taught us this easy mehod of checking if you're fat or not

1. stand naked infront of full length mirror
2. jump up and down and watch your body
3. if you have wobbly parts (at the waist, thighs, arms) then YOU'RE FAT

otherwise you're ok 

Actually, when I was quite lean during 3rd year university. I could use teeth plus gums (don't really know how to explain this) to move my chests/ pecs like those in the kung fu movies.

Now there is a bit too much fat, so have to reduce fat to make it more defined.