Fasting from dawn till sunset without food, water and sexual intercourse may sound a bit daunting at first but hundreds of millions of muslims do so every year and often regularly during the year. 

Fasting is obligated upon anyone able to fast (without illness etc) that has reached puberty.

There are a number of those who are excepted from fasting such as those who are sick or traveling, for those who are pregnant or breastfeeding, for those in old age and lastly for those on their period.