Heh. Every time I go to Japan, coming from the United States, I gain weight. Part of this is because I probably get less exercise while in Japan (since I don't lift while I'm there), and part of this is because I love Japanese food, and so I tend to eat a lot while I'm there.
People who move and then lose weight probably just don't like the food in the country where they moved.
That said, when I stopped drinking soda, I dropped a surprising amount of bodyfat, and felt better overall.
Moving can have a big influence on someone's body/appetite, but moving specifically to Europe has other advantages. There's a book called The French (don't) Diet. I haven't read it, but I know people who have. The basic idea is that French food (and presumably much of Europe's food overall) is naturally healthy. It's not filled with preservatives or infused with high-fructose corn syrup. Those artificial ingredients in most American foods are hard for our bodies to digest, so they move to fat where they are almost never digested. The French food is made of natural ingredients that our bodies can actually use for nutrition and energy, so we don't store the food away - we use it.
The funny thing is that in America, we don't have this artificial food because it tastes better. We have it here because it's cheaper.
On another note, why is this on HN? I know it's tangentially related to the hacker diet, but an Ask YC: How do you lose weight? thread doesn't seem like it would belong here.
Food has to be digested before it can be stored in fat cells. Also, if it's actually more difficult to digest a given food, then you'll get less energy from it, which means less stored as fat. So, basically, easier-to-digest means more fattening.
One large difference between American and European diets is portion size. One study into why the French don't have an obesity problem like a lot of other western nations had the simple conclusion that they simply ate less.
> People who move and then lose weight probably just don't like the food in the country where they moved.
Not true in my case because I moved to France and food is _good_. But I've noticed three important differences from the US:
1. Portions are smaller
2. People eat more slowly
3. Meals are more varied (given #1 it's quite normal to eat starter + main course + dessert in a restaurant because all are relatively small).
I moved from Canada to Spain, ate and drank to excess, but lost 30 pounds in a year. Why? Because I started running, working up to the point where half-marathons were routine. The climate was a contributor, but I think the key was just stepping out of my current milieu into somewhere where I could easily change my lifestyle without any of the old triggers.
People seem to think Japan = Miso, Green Tea and Sushi, but let me present some popular alternatives - Tonkatsu - deep-fried pork cutlet - ice-cream bread (a loaf of white bread with the centre filled with ice-cream) - endless convenience store aisles of two-minute noodle bowl - prized marbled beef (which always looks to be 50% fat!), etc. Though it is true I eat a lot of cabbage here.
Oh, yeah, there's tons of horrible food in Japan. But there's also a lot of much healthier dining options that nominally cost less. For example, I tend to eat a lot of Bi-Bim-Don at Matsuya, with a side of salad. Costs less than 500 yen (about $5 US), really healthy, and tastes great.
You also left out Okonomiyaki, which is not only delicious, but surprisingly healthy. And onigiri...
2. I stopped drinking soda