I was gonna say what tjf said... eat at home first, then when you go get a little pasta and lots of bread, eat the bread, when no one is looking throw the pasta out. Be careful with the soda too, at these parties they are always giving me soda I can't drink and that is annoying, I just get my own water now. Try not to be too anxious about
it all, it is a good start to get out and give this a try, if you don't feel well and need to leave, it's ok. I hope you have a nice time and that your guts behave!