Xenical - Does any one experienced nausea or headache?

Common Xenical side effects are caused by orlistat's fat-blocking action. These are signs that the medicine is working properly. These side effects are usually temporary and may lessen as you continue using Xenical:

oily or fatty stools;

oily spotting in your undergarments;

orange or brown colored oil in your stool;

gas and oily discharge;

loose stools, or an urgent need to go to the bathroom, inability to control bowel movements;

an increased number of bowel movements; or

stomach pain, nausea, rectal pain.

Source: https://www.drugs.com/xenical.html