As a single data point, I live in the US and I've lost ~45lbs over a year and a half by aggressively reducing my portion sizes (to the point where the average m

As a single data point, I live in the US and I've lost ~45lbs over a year and a half by aggressively reducing my portion sizes (to the point where the average meal from a restaurant is comfortably two meals for me), significantly reducing my excess sugar and sweetener intake, and making sure I get a few thousand steps in every day (probably like 5-6k on average). I don't follow a particular diet, I try to make my own meals, and I don't sweat it if I want to have a cookie or slice of cake every once in a while, and it's been really working for me. This was prompted by an annual checkup with my doctor. I was 265lbs (6'0" tall) at 23 and had a number of issues related to my weight, including high cholesterol and an inflamed liver. My last annual checkup, I was down I think 30-35lbs and everything they tested was back in the normal range. So yeah, portion sizes are important.