It's not if you plan on raising a bird for meat, it is if you buy a meat-specific breed. You can raise any bird for meat and a lot of people raise dual-purpose birds for eggs and meat. These birds grow like normal chickens and do not need a special diet.
However, there are a few hybridized...
If you are raising a meat specific breed you need to be very careful with their diet and how much they eat. Otherwise most chickens do a pretty good job at regulating their own food intake and won't over eat.