Body size. Self-Esteem. Diet. Shape and size distortion. Depression.
For me, it is usually: I start worrying that I'm fat, I get unhappy with myself, started hating myself, start cutting back on the amount of food I intake, don't feel it's enough, restrict my intake even more... and don't see any improvement.
In the meantime, I'm sick, nauseated, dizzy, and lightheaded all the time. I get to the point of feeling crappier and crappier every day and then get sick of it.
So I stop.
Am I fat? I don't know. What I do know is that I tend to fall into a bad trap when I start obsessing over food and weight and all of that.
I have also figured out that I tend to maintain or even lose a little when I'm not focussed on things like "let's see if I can't work just as well on fewer calories".