In Islam, Islam is based on (the following) five (principles):

To testify that none has the right to be worshiped but Allah and Muhammad is Allah's Messenger.
To offer the (compulsory congregational) prayers dutifully and perfectly.
To pay Zakat (i.e. obligatory charity) .
To perform Hajj. (i.e. Pilgrimage to Mecca)
To observe fast during the month of Ramadan,
, [Bukhari],
SO, Since Islam means submission to Allah, we have no other choice but to submit ourselves to Allah and obey His commandments. It is from the mercy of Allah towards us that while He prescribed on us fasting He also showed us the greatness of fasting in this world and in the hereafter to make it beloved to us.