You know what when I went on hoilday in August I was really worried about what effect that would have on my fittness and weight. But I ended up being thinner on my return!!
What I didn't take into account was I spend 12 hrs a day behind a desk at work and on hoilday I had to be walking at least 6 to 7 hours a day, plus swimming and other fun stuff, so as a result it offset the hoilday eating. So you maybe surpised how little your hoilday effects your fittness. Of course it does depend on the type of hoilday. If you like sitting in the sun all day and drinking beer all night well that might not be so good.

But many people don't realize that they actual do an lot more exercise in the form of walking etc than they would during the average working week.