Things not to say in front of/to someone who has/has had an Eating Disorder

"I'm just going to go anorexic"
"I'm anorexic for this week/day/etc"
"I'll just make myself puke"
"I could never go anorexic, I like food too much"

There's a difference in having anorexic tendencies and being anorexic, between making yourself puke once and being bulimic, between not eating to fit into a dress and not eating. Don't get me wrong, all of those are harmful, but claiming you have an ED because all you've eaten in 48 hours has been an apple is like complaining about how OCD you are when realistically you just like all your pens facing the same way in a drawer or tend to put your keys consistently in the same place. It's up there with claiming you're depressed because you had bad day, or even worse, telling someone with depression that it'll get better or, that "tomorrow's a new day."
Odds are you don't know what it's like to feel like a failure when you take one bite, to feel awful when you throw it up, to feel even worse if you don't throw it up. There's no winning in this game, but you won't know that until you're certain you're losing and your mind is lying to you saying you're in last place but actually you're the only one playing.
You don't know what it's like to become dependent on the 10 diet pills and supplements you take daily until you forget to take some or decide to stop and get better and you're physiologically not who you were; you are unhappy and mundane, so you have no choice but to revert back to your pills. You don't understand what it really means to suffer until you find out you have permanent health issues, like weak, yellow teeth, and acid reflux that requires long term medication.
The real kick is when you try to stop, try to get better, try to stop taking the pills one by one, eating slightly more, going a day before you stick your fingers down your throat, but you miss something. You're not whole anymore. The scale you hid behind the shelf peaks out and you find yourself standing on it shaking and sobbing. There's really nothing like realizing you've found comfort kneeling in front of the toilet and saving up to buy more pills and feeling empty. At this point, you may even be okay with how your body looks but you can't escape this lifestyle, it's who you are now. When you're lonely and stressed, angry or bored, your eating disorder will always be there to comfort you and there to celebrate with you when you're happy, rejoice with you when you're in love; a reliable acquaintance.
So just be cautious what you say, because it may be the reminder to someone that opens the door to their un-welcomed guest.