There are always potential side effect, the main one I would be concerned about would be shutting your naturally HPTA function and not being able to get your levels back to normal without staying on a small dose. Outside of that most "side effects" can be managed for the most part, with supplementation and research chemicals.
If you have eaten 15k cals for an extended period and could not gain weight then I would recommend getting some labwork done, to check thyroid as as well as everything else while your at it. You can see what your natural test levels are at as well.
I understand that you are focused and 100% on training, we are not questioning that or trying to tell you how or what to put in your body, we are just speaking from experience, at 22 you should already have some pretty high test levels that is kinda why we are stating to wait you should already be making some pretty good gains. So in my opinion I would listen to your friend, get your blood work done, which to me is a staple anytime I am about to run gear so I know exactly where my body/organs are at that time. Then you can post the results here as well if you would like, there are many very knowledgeable members here that work in the health field that can evaluate and also give you opinions on that as well.