If you mean, can you feed them too much and they get overweight? Yes.
I feed mine leftovers out of the house on a daily basis, but it is mixed with other foods too, so they get a good variety. I don't feed them on a packaged complete diet like most people do, it's a mix of "people food" free-range/"pasture" (actually bucketloads of grass clippings from my garden, grass doesn't grow in my yard), spent brewer's grains, and cracked corn. I have a long trough feeder that I keep full just about all the time, it will get empty during the night/early morning because I don't hand out breakfast until almost noon, but it's a buffet all day long.