For one data point, when I studied one year in Ireland, I lost about 5 kilos over the first semester (ending up weighing as little as I ever have ever since puberty), gained back about 2 kilos as (ahem) ‘customary’ during the Christmas holidays back home in Italy, then gained about 6 kilos over the second semester ending up weighing as much as I ever had thus far (though I had started exercising on a regular basis and muscle is denser than fat, so that people back home thought I had lost weight). AFAICT, ‘at first I wasn’t used to the way people ate there, then I adapted’ would be a decent first-order approximation to what happened, though I’m leaving out lots of details.
For one data point, when I studied one year in Ireland, I lost about 5 kilos over the first semester (ending up weighing as little as I ever have ever since puberty), gained back about 2 kilos as (ahem) ‘customary’ during the Christmas holidays back home in Italy, then gained about 6 kilos over the second semester ending up weighing as much as I ever had thus far (though I had started exercising on a regular basis and muscle is denser than fat, so that people back home thought I had lost weight). AFAICT, ‘at first I wasn’t used to the way people ate there, then I adapted’ would be a decent first-order approximation to what happened, though I’m leaving out lots of details.