>you can't exercise out of a bad diet
You can, but it's not easy. People who exercise _a lot_ often have trouble eating enough calories. 5,000 to 10,000 calories a day is hard to eat and not out of reach.
I knew a guy who was drinking a gallon of whole milk a day for a while to try to maintain weight.
I really can't imagine having the energy to burn 10k a day - what kinda workload were they doing?