Every notice how hard it is to make the right decisions when you're tired after a long day at work? According to Dartmouth College researchers, what you're probably experiencing is known as "decision fatigue,"



The researchers conducted a study involving 33 women given two separate tasks. The first task involved watching a seven-minute video with words running across the bottom of the screen, and half of the group was told not to read the words.  After the video had concluded, researchers showed both groups pictures of food and asked them to rate how appealing the images were.

The researchers noted that the women who had to try super hard to not read the words at the bottom of the screen wanted the food more than the group that was free to read the words.
"What we found is that when you have to exert a lot of mental effort to do stuff—maybe you're working on a project at the office or studying for an exam—your brain uses the same resources to do those things as it uses to resist temptation,"

"So basically, making tough decisions all day depletes your brain of the very chemicals it needs to boost your willpower, which is why it becomes harder to say no to tempting foods."
So not only does this brain depletion make it harder to resist tempting foods, it also makes those same foods look even more appealing.  As for how to resist temptation when your brain is completely fried, the researchers recommend removing yourself from any vulnerable situation that would require you to summon too much willpower.