The best thing for anyone to do is to get direction from their Confessor and/or Spiritual Director. We all need to do MORE than what the Church demands of us in order to overcome our faults and get into Heaven.
For me, I had to get direction from both doctors and my Confessor tells me to obey the doctors. Yet, my Confessor was able to recommend other penances that would help in the same way fasting helps.
The point is, we should always be doing mortifications, so Lent should not be some scary deal for us.