FWIW if you're on a trip it might counter-balance: you might be more active with fewer idle time, and the local food might also be harder to fully process. I saw that on a Spain trip where it made absolutely no sense I didn't gain weight touring tapas places for a week.

It was a business trip matching my typical routine. I'd say I was even less active because apparently running in Tokyo sucks.

Also some anecdata, but I think it depends so much on the person: I gained 10 kilograms by living more than a year in Japan.

I ate healthily so I wasn't fat by any means (in fact, I'm really skinny), but I ate so much that I think this is the reason I gained some weight. I ate a lot of rice (my rice portion was usually more than a Japanese person's entire plate).

Every time I'm in japan I walk far more than I do while in the US. I also end up going up stairs a lot more than I ever need to in the US. Good public transportation makes a huge difference.

I'm euro and runner/cyclist so I doubt that was a factor. I also had my bicycle with me for some rides on off days, but it wasn't beyond my usual mileage. Maybe even less, because riding road bike in Tokyo was an experience that made me realise how good I've it back home. Surroundings hills are nice, but getting out of the city sucks big time.