Diet as "great" needs to be quantified. In reality as long as you eat more calories than you burn, any diet can be "great." It is impossible for the human body to build actual lean tissue without enough calories to do so. It's like building a house with no bricks. Now if you want to get fancy, yes, there are better foods, and yes, eating plenty of protein is what you need to build that house. But retarded training is probably more common than retarded eating. This is why "prisoners get so jacked." They eat a ton of calories, it just comes from shitty processed junk. Which I try to avoid at all costs, not being in prison and all, and having the choice to eat well. At the end of the day, train hard/intense and allow your body to recover while eating at minimum a few hundred over what you burn (with 1 gram per lb or bw in protein minimum). Whalla, growth.