Eat less, fast, work out.

For sure portion and lifestyle (walking) differences, but glyphosate is a big player too (at least for grains). My wife literally cannot eat grains/bread or cheese in the USA. She gets sick every time. She is complete fine when we go to Italy and eats everything. 

Pasta/pizza/pastries nonfungible between countries 😄 

 Placebo effect 

 Test it out. Serve her some imported Italian food, tell her it’s American but to see if it still upsets her stomach. She will eat it and be like omg I’m so sick I told you I can’t 

 😂 we’ve tried but I’ll give it another go 

 You’ve tried to trick her and test the placebo theory? No