While she enjoys acting, the “Twilight” actress admitted that she occasionally gets stressed out and it can impact her weight. "I'm a little bigger than sample size when I'm eating cheese burgers and am happy and comfortable. If I'm stressed or working, the weight falls off. My weight and my sleep are tied to my nervous system. Sometimes I'll sleep for 12 hours a night and sometimes sleep just doesn't exist for me for a couple of months," she said.