Is there anything to worry about?
Yes there is. In fact, if you abuse the use of fat burners then there is certainly a lot to be worried about. You would be preparing yourself for side-effects which could be short-term, long-term, reversible or irreversible. Sounds horrifying? It is intended to be so because unless you use these things under proper guidance of an expert or medical practitioner, you are making a good case of what not to do. There have been cases in the past when people go to extremes in their desperation and suffer from side-effects. It is generally not the product that has to be blamed but the greed of the user for overnight success.