The Science of Fasting

I have a random question for this group. I kind of figure this is a good place to put health and fitness related stuff so apologies if it's detracting from the purpose.

There is lots of information 'out there' suggesting that all you need is to be in a calorie deficit to lose weight - which is kind of true - and that if you're lifting weights and in a calorie deficit, you'll lose weight and lean out.

This is not the case for me. I will easily pack on muscle and I won't get fatter but I will not lean out. I just pack on muscle, retain my fat and that's it - unless I also incorporate a good amount of cardio. Why? I guess it's just irritating to me to hear "just lift and eat in a calorie deficit and you'll lean out" - not for me.