I don't think the OP was saying they'll let her go because of her weight and age, I think she was asking how hard is it going to be to get another job at that weight and age.
You know, I'm pretty sure it's going to depend on your skill set, recommendations from previous employers, and the economy in your area.
I would get as many letters of recommendation together as you can right now from your boss and maybe your boss' boss if you worked with that person enough for them to write one. It's always harder to get one once you aren't around them anymore and since they all know you're likely to be laid off soon it's not like you're trying to abandon ship or anything.
I wish you the best of luck, hope you aren't laid off but if you are I hope you find another position ASAP.