While it depends on what feild you are in, most employers will look past the weight. They look for a clean, neat, well kept appearance. It gives the impression that you care about yourself and thats transfers to you will care about your job. (I'm not sure whether I made sense or not)

I agree with Direction, when explaining the breaks. Keep it simple and general in nature. In fact people are more inclined to give a deeper answer than needed. It when you think about the details that you need the kleenex so stay away from your trigger words.

While it sounds trite and overused...Get a good night's sleep and breathe deeply. Listen to your favorite music. Do whatever you need to help relax.

Remember also, the person interviewing you knows that you are nervous. Don't expect perfection from yourself...your human. If the interviewer is good, he/she should help you feel at ease.

Will be keeping you in my thoughts.
Good Luck