In my pursuit of weight gain, I might have to switch over from a nearly pure protein shake to a weight gain shake because I'm almost always hungry and staying +- 1lb since mid-December. The protein shake I am using (Mutant Pro) has only 120 calories with 2g carbs (1g sucralose), and 24g of whey protein. Because I'm the skinny guy with a fast metabolism (ectomorph), it could simply be that I am not taking in enough calories per day.
Looking at Mutant Mass as a weight gainer, which has 1,100 calories, 192g carbs (18g sucralose), and 56g of whey protein per shake. I could split the serving size in half to take two shakes per day rather than chugging a litre (32oz) at once.
I think I'm simply burning more calories than I consume. Changing my "food diet" isn't really viable as my wife has the opposite body type and metabolism and I want us to have the same meals together, even though we have opposite goals. BTW our meals are almost all fresh veggie with some fish/chicken thrown in.