I am not quite positive but I think that the Yulia's doctor would most likely tell her that the reason why she has begun to gain weight is because she has stopped growing. For example, when Yulia was younger her body needed more food to keep up its strength and to help her grow but now that Yulia has stopped growing Yulia doesn't need as much food as she used and should, therefore, start eating less and start eating a bit healthier.
I hope this helps
