Could obsession be related to my eating disorder?

Eating disorder. Yes there could be an association, and this often occurs. It is important to discuss these worries with your doctor and to be seen frequently until you are well.
Yes. Eating disorders often include obsession with food -- either avoiding it, or consuming large quantities of it and then purging one's self of it. There may be very specific patterns with it; extreme control and thinking about it a lot. Numerous studies have shown that people with eating disorders have statistically higher rates of OCD (11% - 69%).