How to effectively respond to harsh suggestions from the faculty of review committee? As generally expected the doctoral review committee has to evaluate the PhD student by asking questions, by debating etc.,

Faculty in doctoral review committee can give soft suggestions and are capable to provide grade for student for that particular semester and can even fail the student. 

All the above are not insulting since all are dependent on performance of student.

But how to respond to the intimidating comments by faculty in the committee that are harsh and targeting personally, which are not deserved for a doctoral student?


  Example for harsh suggestions includes follows:
  
  1) Don't roam outside too much, sit and do work silently;
  
  2) Better to eat less and work more;
  
  3) It is not worth for you to do this degree;
  
  4) Can't you understand the content that bachelor degree students can
  understand?
  
  5) The work done by you in this semester can be done by masters
  student in a week.
  
  etc..,
I don't know what is the norm in your institution, but I would characterize comments 1-3 as highly inappropriate and unprofessional. The committee should not comment on a student's work and social habits, their eating habits (this would be considered taboo in many places), or offer dismal views on their prospects after a PhD. In my department, making comments like this towards a student will, at the very least, be cause for a very unpleasant talk with the department head, and will require a written apology to the student.

Criticism on your progress or your understanding is definitely acceptable, but can be conveyed in a more conducive manner (e.g. by not comparing your understanding to that of undergraduates - offensive to both you and to undergrads). 

That said, if you receive these kinds of comments, you should speak with your advisor and see what you can do to make things work better. Comments 4-5 are simply a rude way of saying that you aren't making sufficient progress.   

If you feel comfortable with your advisor, and assuming a culture of abuse is not prevalent in your department, you may raise this issue with them. I for one would be furious to hear this and would probably confront the offending committee member myself. If not - try to contact student affairs. 

Abuse towards students should not be tolerated.