Whether you're a beginner scrounging for cash, or a forgetful rancher with fat monsters, this is something you need to know.
While doing some tests, at the second week of starving my monsters started taking a 4%-5% fatigue hit! The number added may have increased through time, but these monsters were rested each week. So be sure to keep your monsters well fed, and their weight in check. Also, make sure you always have something to eat.