What Lawrence is is too healthy-looking to play Katniss. And so are her male co-stars.
Suggesting that Lawrence is in any way fat is ridiculous. She isn't. But in the book, when the Hunger Games conclude, Katniss's desperation is palpable. While Cato is dying, Katniss is suffering from hunger, from thirst, from exhaustion. Peeta is also injured and has been sick--although he received medication, he has not had time to recover fully. Neither has bathed since arriving in the arena. Neither has slept properly since leaving District 12.
And yet, the film depicts both with perfect skin, clean hair, and the ability to stand erect while waiting for the hover planes to get them.
Given that the books are about suffering, it seems a poor directorial choice to cast beautiful, healthy and strong young people in the three pivotal parts (Katniss, Peeta and Gayle.) All three are meant to be attractive, of course. But all three are also deprived from a life of living in a depressed District. (Peeta less so because his parents are merchants, but still.) Katniss and Gayle hunt squirrels for sustenance and we're meant to believe that they needed to put their names into the Hunger Games lottery extra times in order to survive. Based on the movie, I don't buy it.
I suspect the movie's producers were just cowardly. They wanted to make a movie trilogy from a popular book trilogy, but they were afraid that if they made their stars look hungry, tired, injured and desperate, they would no longer be sex symbols. After all, a woman (especially a young, beautiful woman) can't be expected to appear on screen with less than perfect hair, can she? Never mind that she's been running from fire, struggling with bees, wrestling with knife-wealding enemies and saving Peeta's life--the important thing is that her hair is perfect! And, lest we accuse them of sexism when their real crime is image-ism, let's not forget that Peeta managed to remove every trace of mud and dirt from his body after painting himself in fully detailed camouflage.
It seems there was a whole lot of shallowness and stupidity involved here. But that doesn't excuse calling a healthy girl fat.