How do i say no to junk food politely...without offending?!

How do i say no to junk food politely...without offending?

example last night my sister bought peanut butter whoopie pies...two servings in each pie 390 calories 23 grams of fat in each serving....so if i ate one it was twice that! i said no...to it but she got all bent out of shape and upset over it...its hard for me i am trying to get into great shape for my hubby when he comes home from Iraq...i don't want to eat anything that isn't healthy but my sister gets annoyed if i don't eat it...?

1 day ago
then she feels bad like she shouldn't be eating it...but its just that i don't want it

1 day ago
thanks guys! u know how it is...i don't want to hurt anyones feelings you know what i mean? i love my sister

i do it all the time. my students always bring me crappy junk food to eat and i just politely tell them no thank you i don't eat packaged food. too many preservatives, calories, fat, take your pick. eventually they got it and realize that i just try to eat healthy.
your sister will get over it. just keep reminding her that you're eating healthy for you and your husband.