Whether you get fat and flabby while you're travelling rather depends what sort of trip you're on.
Most of the journeys I make are pretty active, with lots of walking, and the food is usually tasty but plain, heavy on vegetables and rice or noodles, low on fats and cholesterol. I often lose weight.
But now and again there's a trip that involves a lot of sitting in cars, buses or boats and eating lots of fabulous rich food and wine. There goes the waistline.
Of course if your journey is an inactive one you can exercise - if there's time - but when you're in a strange place it's often hard to know where to go.
For instance, until my knee packed up a couple of years ago my main form of exercise was running. But how safe is it to run in New York or New Caledonia? And where can you go in Beijing or Bangkok without being asphyxiated by exhaust fumes?
Fortunately there are now an increasing number of websites which offer advice. A good source of information for runners is run.com which suggests 12,000 running routes in over a hundred countries.
Following my usual practice of testing the accuracy of advice by looking at places I know, I checked out New Zealand where there are 66 routes listed, 31 in Auckland and one in Devonport. The ones I looked up seemed great. In fact I'd run some of them (including the excellent Devonport route).
As you'd expect the options vary from country to country. There's only one route on offer in Lebanon or Zimbabwe but 177 in Italy and, impressively, 544 in Singapore ...
Of course a lot of people prefer to work out and the big trick there is to find a hotel with a good gym.
I found a story from the Associated Press about Matthias Morel, an airport marketing consultant who travels a lot for work, and has grown irritated with finding himself in hotels where the gym is in a converted guest room crammed with out-of-date equipment, or a windowless basement cell with no air-con.
So he and three partners started a website called hotelgymreview.com where users can review their hotel gym experiences and find the best hotel gyms when they are travelling.
It's a nice idea but the information is a bit patchy. If you're visiting New York there are plenty of suggestions: the top-rated hotel is Doubletree Metropolitan Hotel New York which gets three stars (gym users are obviously fussy).
But when I tried to test the accuracy of the information by looking at Auckland hotels not one had been reviewed. And in Sydney there were only two reviews: both of them, Novotel Hotel Darling Harbour and Amora Hotel Jamison, got three stars. I guess it'll get more useful in time.
Other options suggested by the AP story include:
More than a million hotels, including DoubleTree, Hyatt, Marriott, Hilton, Omni, and Radisson, provide in-room workouts through the cable station Exercise TV, but none of those chains have it in every room so you need to check when you book.
Selected Marriotts will set up a Wii Fit on request; some Westin hotels have exercise equipment in selected guest rooms; Sheraton hotels offer free "workout in a bag" kits, with a mat, stretch rope, and other items for guests to use in their rooms; but, again, it pays to check.
And if all else fails, Jennifer Galardi, a dance and fitness trainer for Exercise TV, believes you can get a good workout anywhere, even without a gym.
"There are a number of things you can do without equipment," said Galardi, who often works out using hotel furniture, including chairs, for leg-strengthening squats.
"I think people get spoiled. They're used to the best and the latest equipment, but you don't need it. Actually the older things are better because you need to work hard to make them work."