I guess I'm having a hard time relating to the angst over possibly not being to eat much... or anything... at a wedding dinner. It's only one meal, and it certainly wouldn't hurt me to do without a meal now and then.
I try to keep something with me to fend off "starvation" if I can't find something healthy for many hours. Lately I've been carrying either a zip-lok bag with several Wasa rye crackers, or a handful of almonds. When I'm at a function or restaurant or friend's home, and can't find something acceptable, I will just snack on my "bring-alongs". Usually I can get a cup of tea, maybe some salad or something as well.
To me, it would be very bad manners to submit a special request for a wedding dinner or buffet. Maybe I'm old fashioned, but I was taught to either eat or not eat what is put in front of me, and to NOT comment either before, during, or after if something is not to my taste. Just don't eat what you don't want, and don't make a fuss. Mostly, people don't even notice. If someone does, simply say you don't feel hungry.
It's different if it's a restaurant or airline or some entity you have PAID to provide you with a meal. Then you can request, demand, complain etc. This simply doesn't apply to social occasions, however.