Why do skinny people get bullied?

Answer: Fat girls become targets for ridicule as they appear comic and may appear funny when they walk or do some activity.It is common in social groups for dominant people to pick on the weaker ones.Not only fat girls but skinny girls are also ridiculed

Answer:

Obesity is frequently a symptom of emotional insecurity and low self-esteem. Aggressive people tend to target victims who they perceive to be psychologically weaker than themselves, as they are least likely to successfully retaliate. No matter how much we might wish to think otherwise, a lot of human behavior comes down to a competition for mates and one way to the top of the ranking is to marginalize all competitors.

Incidentally, obese boys are somewhat less likely to be bullied than girls, because of their physical dominance in the peer group.