I will always disagree about performance on high fats low carbs however. Glycogen levels are important yes, but that has nothing to do with where the majority of your calories are coming from throughout the day. The OP was asking about putting on weight not running a marathon. Would it be stupid for a marathon runner to go low carb right before his race? Yes... The point I'm trying to make is adding quality mass doesn't require shit loads of carbs like so many believe.