I mean you can visit Tokyo and barely notice anyone being fat while in New York there’s about 30% people being obese, even though both countries have fast food. Although Japan has less of it tending to burn off that by walking or exercise (it also reflects their lifestyle) and portion sizes regarding food & calorie intake while in US there are literally multiple fast food joints next to each other along with huge portion sizes.
When we were in Tokyo and SE Asia, we lost weight. The food is lighter, healthier, smaller proportions. The rice is not handed out like some sort of endless buffet. You get a cup of rice or whatever the measurement. That’s it. No additional servings of rice. Andrew Weil did a whole description of how cultures who’s staple foods (rice, corn, grains, taro…) have become more finely processed become more obese, across the board, as a culture. When it becomes fine powdery flour, it breaks down into sugar way faster. You’re not supposed to eat that shit for good reasons. Lifestyle plays a big part but cutting out all that junk food is critical.