For me it can vary a good bit. Not counting food itself and fuel I can usually fit everything in a 2 liter stuff sack these days. I generally carry very little food and maybe 12 ounces of fuel (alcohol). Even back when I packed really heavy and carried cooking gear for three on my first tour, I can't imagine ever needing more than even a small pannier for food, cooking stuff, and fuel.
The exception might be if I go bike packing or touring in a more remote location that required more than a few days of food or maybe a bear canister. Still even then I could probably manage with normal sized front panniers if using my small bear canister.
Last edited by staehpj1; 01-08-14 at 01:24 PM.