Wintergirls Title Headings?

I am currently reading the book Wintergirls by Laurie Halse Anderson and the chapter titles are confusing me a bit. All the chapters are titled 001.00, 002.00 and so on. I think that this has something to do with eating disorders but even though I have had an ED for many years I still cannot figure out what they mean. I would be grateful if anybody could tell me :)