I would suggest you read the great Kate Harding’s words on the subject:
She has laid it out much better than I could ever hope to.
There are also a ton of resources in the link on the side panel of the blog:
And take a peek through the health and resources tags for good measure!
I will be making some changes around here to make this kind of info more accessible (like an FAQ, more organized and detailed links page, etc.) but I do tag everything like a maniac - this blog has turned into an arsenal for my own learning process on everything, including fat health.
The best way to know how to come back at anyone in these arguments is to educate yourself on the subject as much as possible, assess the situation and relationship you’re trying to introduce this kind of dialogue into, and formulate a way to respond in your own way. When all is said and done, you will know the best way to go about it.
Know that your friends may not agree with you or find it hard to swallow, so go into it positively - but prepare for a possible negative reaction by knowing that some people need time to understand. Hell, some people will stare cold, hard facts in the face and refuse to acknowledge them. But you see the facts, you know what’s up, and that’s what’s most important. For you.