I don't think most professionals today judge a qualified person by their weight unless it is a physical job that requires them to be in good health. I think the fact that you made it to the interviews is a sign that they considered you seriously. If they hadn't, you wouldn't have made it that far. Only so many applicants are chosen for interviews.
In two different jobs, I worked as an assistant to supervisors who asked for my advice on who to hire. I also had to sort out the resumes according to their requirements, and for the interviews. On one job, the applicants were required to supply a photo because they would be working with the public (i.e. a good part of the job was as tourist info reps). Those that didn't supply the photo, didn't get considered at all. So while most jobs don't need a photo, if they ask for it -- give one.
They just wanted to make sure the applicant dressed in a professional, neat & clean manner. Since they had over 400 applicants for about 20 positions, they used "requirement criteria" to weed out those who didn't follow instructions -- and this is a tip that everyone should remember. Many applicants don't get interviews because they didn't follow instructions at the base level. Also, if the application and resume were messy and incomplete, it was canned. Get it done professionally, if needs be.
I agree that showing eagerness is important. Don't be afraid to ask a few questions -- that shows keen interest. Plus, make sure that you are as qualified as possible: focus on any skills, talents, education, or experience that could be helpful in that position. Include volunteer work and any clubs you belonged to (i.e. Girl Guide leader; coaching sports; Big Sisters) --- that shows a social interest that would be admired.
EDIT 2 ADD ~ Btw, if someone doesn't want to hire you just becuz of your weight -- trust me, you wouldn't really want to work for them either ...
