Thanks for posting your query at DoctorSpring.com
I am Dr.R.K and I am pleased to assist you.
Sovaldi does not cause weight loss. But Ribapak may cause weight loss.
But weight loss even after almost 2 months of being off these medications cannot be attributed to them.
Give him nutritious diet. In spite of enough calories if he is losing/not gaining weight then further evaluation should be done.
HVC infected individuals can develop cirrhosis and liver cancer also.
Get an ultrasound scan of the abdomen and serum alpha fetoprotein test done.
I hope that answers your question.
Let me know if I can assist you further.