Apparently, that are now good points.
If you get a place with bad diarrhea and terrible food, weight losss is guaranteed. Alternatively, high altitude or fervent walking/hiking are also good things. When you have altitude sickness, you feel nauseous - and you can't eat. And if you are nauseous and hate the food (think yak meat??), you are on a crash diet. And you think you can cheer yourself up with chocolates? No way, at most you can get is a bottle of Coke in the region.Combine that with no real transport other than your two fat legs - heaven. And yes, heaven would be near if you are in Tibet in a hiking holiday, or Machu Picu.
This is the top weight losing holiday destination - (they key to sucess is to chose the cheapest package you can lay your hands on)
1) Tibet
2) Machu Pichu
3) Eygypt
4) India (Bump this up the list if you cant eat hot food at all)
For Tibet, a few people or their friends lost 6-8 kg from constant walking and no apetite in 10 =14 day trip. Similar case for Machu Picu
For Eyqpt, you could lose 3 -5 kg a week, if go cheap and WALK more.
For India, the example was stay a month and you might be 10-20 kg cheaper. It goes to bottom of that list because some people did not lose any weight on short trips (and possibly good hotels)