I am looking for a single word to describe a person who does not discuss a few topics. He/She does not sidestep the topic, he/she frankly tells that they do not want to discuss that particular topic.
e.g. If you ask person X about topics like world news, today's weather, past relationships, etc he/she freely discusses them. But if you ask that person about his/her food preferences, he/she responds saying that, "I do not want to talk about food preferences ever again."