Hey..
Ok this is one of those very girly questions but was wondering are you more likely to pile on the pounds or shrink your waistline while on a RTW trip!?
Having put on a few pounds myself I am hoping that i will get back in shape whilst away thinking that i will be getting more exercise and eating less on the big trip!?
I personally find that I tend to lose weight when I travel for pleasure, mainly because I am out walking a lot and I do eat less. I eat less because I don't find myself snacking out of boredom like I do at my desk job.
The only place this wasn't true was in France, where I ate pastries every day for breakfast and put on 10 pounds.
I think it depends where you are. In Asia I lost weight, not through getting ill, but I suppose through eating so healthily as well as all the extra exersise. 
Then there's what I've heard called "the Sydney Stone". You get to Australia, after being somewhere like Thailand and suddenly everythings really expensive! When you're dealing with scabby hostel kitchens, trying to buy food that you can travel around with and don't need to add much to, and living on a very tight budget its hard to eat great. Most people I knew lived on Pasta. And lots of alcahol.... So you put it all back on.
But after Aus and NZ I went to India. I was convinced i come back skinny as anything, after suffering weeks of stomach upset....But somehow I ended up totally fine, in fact to be blunt and sound like Dr Gillian McKeith- I've never had such healthy poos. 
And, like someone on "you are what you eat" I still came back really slim. Unfortunatly, returning to unemployment and the longest winter in years, being bored and depressed meant I piled it all back on and some. 