One cold day we went climbing on some remote mountain roads and some brought Camelbaks to carry extra food and water. Up around 7000 feet one guy whips out some big slices of leftover pizza. Man, it looked good. Sometimes I would bring one of those big banana-nut muffins. They're about 500 calories and my stomach likes them.
In 1990 I did loaded touring and I ate about 6000 calories per day and still lost weight. This was while doing 80-100 miles per day.