adj. Promoting or encouraging excessive thinness, extreme weight loss, or anorexia.
Also Seen As
The group dieting that is relatively ad hoc among friends and sorority sisters takes a more organized form on the Internet, where spring break has become a popular topic on Web sites and message boards maintained by devotees of a controversial underground movement known as "pro-ana," or pro-anorexia, who sometimes identify themselves in public by wearing red bracelets. There are hundreds of pro-ana Web sites promoting and supporting the "anorexic lifestyle," despite aggressive efforts to shut them down by eating-disorder activists.
—Alex Williams, “Before Spring Break, the Anorexic Challenge,” The New York Times, April 02, 2006
Pick up any gossip magazine, and you'll find a pic-filled spread. "Stars: Are They Too Thin?" they ask as every pound of weight-gain is breathlessly heralded as "a return to curves." These pictures usually make their way onto pro-ana (that's anorexia-promoting) Web sites, where they're tagged as "thinspirations."
—Mark Ellwood, “Is thin in?,” New York Daily News, March 09, 2006
2001 (earliest)
Health experts are calling for a ban on "sick" websites that use skinny stars such as Posh Spice and Kate Moss to promote anorexia as an acceptable "lifestyle" choice.

The so-called Pro-Ana sites offer tips on achieving "beautifully emaciated bodies".
—“Anorexia web fear,” Scottish Daily Record, February 14, 2001
A similar adjective is pro-mia, which describes people or websites that promote or encourage bulimia.