I'm surprised no one mentioned beer. If you want to get fat drink beer. It works great.
Also eat out alot, fried chicken, french fries and burgers lol. .Someone mentioned McDonald's but after I eat that I shit out all my fat and some of my intestines too. That stuff is potent laxative man.
This way you can increase fat reserves, but all this is too harmful for the body. It is better to eat nuts, avocados, butter, fatty fish. From drinks, milk, kefir or yoghurt is good.