The interviewer who asks this question is probably more interested in knowing your motivation and also to check if you know what you are getting into.
When talking about your passion and determination to enter a new profession, one should make sure that the use of body language and tone of voice should corroborate with the spoken message.
A good response to this question should demonstrate to the interviewer that you have thought about the pros and cons of the career path rather than falling into something that you are unaware about.
Most interviewers are used to dealing with fresh crowd, so it could also be a first time experience for them.
Demonstrate in your response that you are very much determined about the shift of the career.
Construct your answers in such a manner that it shows the time and effort that you have already invested in researching your new career choice.
Thus, the candidate should be prepared to talk about the career future. If one is changing careers entirely, then one must assure the interviewer that you have given the matter a lot of consideration and are ready for all the psychological, practical and financial aspects of doing so.