I can understand why carbs are good PWO, but on rest days is there any good reason to include carbs in my diet if I can get adequate calories from just fat and protein? I am 26, 5'11", 160 lbs and trying to put on mass. Thanks!
If your goal is to gain mass eat carbohydrates every day. There is absolutely NO reason, given your aim, not to. Big protein, big carbohydrate from starch, moderate to maybe lowish fat. You'll have high energy, good performance with the iron, and you can raise or lower the fat-intake to control body composition
Yep. Like the others said, carbs everyday if you want to bulk up. You will put on some fat, but that comes with the bulk you say you want. If you keep it to the good carbs and not junk, the fat gain should be fairly minimal.