If you eat 10lbs of food would you weight 10lbs more on the scale?

Thanks for the responses. The reason why we can’t weight the food before hand is because we were doing it at a restaurant, also food with standard sizes can be accounted for like hot dogs, we were challenging ourselves to the number of olive garden pastas but since each portion is different, was trying to find an easy way to determine the amount of actual food eaten in case of a tie.

Also for stuff with bones, like ribs, just because ribs weigh 10 pounds doesn’t mean a person will eat 10 pounds of ribs. I suppose you can weigh the bones later to determine the actual amount of food eaten. We were looking for an elegant solution to this problem.

It’s probably going to be more accurate to weigh the food, and should be pretty easy. Get a food scale like this one, which is small enough to slip in a purse and could easily be brought out at the restaurant. Weigh the plates when they are brought out, and when someone is finished eating on that plate. If more food is added to a given plate, just make sure to weigh it immediately before and after the food is added.