For a three-day trip, it really doesn't matter. For longer trips, that's different. If you're the lean and hungry type, it makes more difference. For me (definitely not lean, and usually too tired at night to be hungry while backpacking) I take as much as I can manage to eat, which for me works out to a pound of food per day (if I'm using freeze-dried instead of dehydrated fruit for snacks, which I do only for trips over 5 days). I do nibble nuts and dried fruit at frequent intervals during the day (labeled as "lunch"), probably why I'm never very hungry at dinner. When I get hungry is after the trip when I unfortunately no longer need the excess calories!

I do like to take food that is palatable and nutritious, though, which is why I avoid commercial freeze-dried sawdust dinners like the plague. If I took those, I probably wouldn't eat anything at all at night! Your mileage (or at least your taste buds) may, of course, vary!