IMO, most of 'em do because they contain some sugar and carbs. sugar gets into you the fastest, so if you want an energy boost quick, that's what you want. Nuts and sausage have a higher calorie content per unit weight because they contain lots of fat - in the context of
having energy this isn't a bad thing - but while the fat in these will eventually give you energy, it won't do it as quickly as a good old fashioned sugar rush. Hence my reason for carrying high sugar
energy bar snacks (Hey, a mars bar even says "energy bar" on it <img src="/forums/images/graemlins/wink.gif" alt="" /> along with nuts and sausage and dried fruit. I find I do well with small snackings on those nuts and the like with the occasional sugar
boost of a candy bar.