Should a person Fast on Yom Kippur ?

Answer 
From what we know, Yom Kippur Fasting is the only Biblical Fast Day. It is Positive Mitzvah # 164. It is written in Parashah Acharey Mot. Leviticus 16:29 "In the seventh month, on the tenth day of that month, you must afflict your souls" 

All Other Fast days in the Jewish Calendar are Rabbanical. 

Fasting helps to keep the mind focused as one doesn't have to worry about eating. It is to put oneself in a better frame of mind, so one can commit to being a better Jew, a better servant of God and a better human being. If one can do all that without (fasting) afflicting oneself, great! 

There are 5 things that are forbidden on Yom Kippur. They are:

1. No eating or drinking
2. No washing or bathing
3. No anointing the skin with oils
4. No wearing items if made from leather (jacket,shoes,watch)
5. No marital relations