There are places on the Internet that prey upon teenage insecurity and pose a real threat to girls who are unhappy about how they look.  They are websites that urge teens to lose weight at any cost.The sites carry images, messages and how-to advice on how to get skinny, including simply not eating."When someone goes to these sites, it's like their food.  It's like their breath.  It's like their life," said Cheryl Kerrigan, who has written a book about her 30-year battle with anorexia.The blogs encouraging girls to get skinny are known as "thinspiration" blogs.  Some of the young women posting to the blogs have user names such as "Pretty Collarbones," "Battle for Thin" or "Melt Myself Away.""It's entirely obvious as soon as you start to read through these websites what's going on, and it's very, very scary," said Dr. Stuart Koman with the Walden Behavioral Center who treats eating disorders.Koman said the blogs seriously undermine the recovery for those suffering from a disorder."They can be fairly militant, besides providing lots of info about how to lose weight, how to show more bone and how to hide what you're doing," Koman said."They are extremely dangerous because it feeds the eating disorder.  It feeds the distorted eating," said Kerrigan.Kerrigan said the last thing anyone with anorexia needs is encouragement to avoid eating.  She said the blogs are outrageous and life-threatening."You're getting false positives.  You're feeling empowered.  You're feeling like you're doing great work because the eating disorder is telling you to get thin and you'll be happy, get thin and you'll be popular and you're doing all the tips the blogs are telling you.  Unfortunately it's a spiral downward," she said.The blogs have been around for years, but with smart phones and iPads, access to them is easier than ever.  That's why there is so much concern."The most important thing is to get some professional support and help," said Dr. Rebecca Wysoske, a psychiatrist at the University of Nebraska Medical Center.She said family support is also vital."That's always a much better place to get support -- from people who are trying to help them overcome the eating disorder rather than helping them support the eating disorder," Wysoske said."It's like quicksand," said Koman.  "The more you go down that road, the more time that's spent on a blog, the worse it is."Tumblr, the Web company that hosts the blogs, is in the process of figuring out what to do about them.  Among the ideas Tumblr is looking at, is allowing users to vote whether the blogs should be banned or to make users watch a public service announcement about eating disorders before accessing the blogs.