. >> reporter: meet sheba. for the last few years, his rife has been about sitting around and snacking. and he's got the belly to prove it. he lives at the national pry mat research center, where he and others are fattened up for science. so, this is bashful? >> this is bashful here. he's a middle aged obese monkey. >> reporter: sheba, along with bashful, cuddle bug, kasper, good looking and chris farley sit around all day eating junk food, locked in cages, doing nothing. you're trying to make monkey just like the human couch potato? >> correct. we are trying to model that sedentary lifestyle. >> reporter: researchers here, who study the effect of food on the brain, maintain that they've already made key findings. like how diet seems to impact a baby's neurological development. watch this baby monkey, just 16 weeks old, whose pregnant mother was fed a high fat, high calorie diet. confronted with a strange toy, in this case, mr. potato head, she becomes anxious and runs away. but now watch the baby of a monkey f