The fish and chips example was a huge exception. To fit that in in this scenario I'm forfieting what I'd normally eat, which might well be some meat or carbs or that stuff you're whining about (I'm not an athlete btw, I get along fine with very few carbs, nobody needs me to run anywhere). This is exactly why I don't eat fish and chips... (although I've been known to split one portion with someone else, that makes it not too bad).
And if I had 2000 calories in a single day that would be pretty bloody catastrophic. I'll only exceed that on very special occasions.