The guy is taking 50+ substances and yet it is unfathomable to some that he may have a positive change in appetite.
Stop thinking about the vitamins role in metabolic function think about the other things they may be changing. Pick any one of those 50+ substances and you will find other functions or side effects of each one. Take Calcium carbonate as an example, it is a simple inorganic salt. Now the main reason it is there is for the calcium ion; I am sure you are well aware of calcium ion channels etc. However, it is also an alkaline substance that will raise the pH of his digestive system (goodbye heartburn) and also will increase the CO2 concentration in his blood stream (which increases the buffering capacity of the blood). Think about it... these are side effects; not the reason they put it in. Now this is one of the simplest compounds on that list; pick something more complex and look up side effects.
50= substances and which string is being pulled? All of them!