I think this is a very interesting claim that you have made, and I believe it to be true. While you claim that 1 in every 5 boys "may" have an eating disorder, and it is not definite that they do, that is still a strong claim and is true. You cited a credible source, People Magazine, and the article is by Cara Shultz, who is an author/writer/reporter. People is a very popular news source, and Cara is a known writer/reporter who works for them, so there is no doubt that the research was well done. The article also cites other sources along the way, quoting them and linking their websites which helps the reader to gain more insight and gains the page more credibility. Overall, I believe this claim to be true.