When my wife was working in NYC, she gained weight considerably, with her normal eating portion. After she went home back to Japan, and still had her normal eat

When my wife was working in NYC, she gained weight considerably, with her normal eating portion. After she went home back to Japan, and still had her normal eating portion, she lost her weight. At the same time, every time I visited Japan for 2 weeks I usually splurge daily, above my normal portion, and I did not gain weight at all. I might've even lose some occasionally.