I had no idea how shitty fast food (McDonald's, KFC etc) was making me feel until I recently gave it up. I'm trying to eat healthier (and vegan-er) so the first thing I did was give up my fast food habit. A few things I found interesting about the process:

1. Holy shit is this hard. I don't know if I'm just weak-willed or they put some seriously addictive stuff in there but the cravings are almost unbearable.

2. Other than that I feel amazing after only a month. I have more energy, a better mood, my digestive system is better, I look healthier. All this makes the cravings worth it and those are slowly getting less terrible.

I highly recommend giving up fast food.