We all know fast food's bad for you.  But here are five ways that it's seriously messing with your BRAIN . . .

 1.  The golden arches are designed to make you hungry.  The combination of bright red and yellow somehow jumpstarts your metabolism. So you automatically get hungry when you see a McDonald's sign.

 2.  When you eat fast food, you have to keep eating it . . . or you'll get depressed.  Studies found that eating a high-fat, high-sugar diet changes the chemical activity in your brain. And if you stop, you'll get anxious and sad.

 3.  Fast food can be as addictive as drugs.  There are tons of studies about how eating fatty, sugar-filled foods can lead to compulsive behavior and stimulate your brain the way hard drugs do. The studies are usually on rats and mice, but still.

 4.  Fast food makes it harder to appreciate beauty.  Researchers claim that just SEEING fast food logos can limit your ability to appreciate art and music.  Because now you're more restless, and geared toward instant gratification.

 5.  You can't make good financial choices.  Researchers interviewed people about money, and the people who were standing near a fast food restaurant during the interview made the worst decisions.