I've only been overweight once in my life and that was after cancer treatment and now back at normal BMI. Most of my life had BMI around 19-22.
Do about 4 hours of physical activity a week - swimming x 2 or 3, gardening, walking round gardens, did a 2 hour walk today. Aerobics and gymnastics when younger.
Foodwise I have always been careful re calories and never drank much at all, a glass at Christmas or special occasions. Weighing yourself say once a month can be helpful so you notice quickly if there's an issue. When I was up to mid 40s it was very easy to stay thin, after chemo induced menopause I had to be careful with sugar and less calories. I also hate my appearance if I put on weight so that motivates me. If anxious my default is to not eat. Do have fair amount of takeaways but will make sure they include a reasonable amount of veg (today's was Toby carvery roast). Losing weight the time I had to I was very strict on a 1,200 calorie diet (plus ate back exercise calories), and minimal sugar or salt, don't like salt so that was easy, only drank water with lime juice or tea with no sugar and have carried that on other than odd drink. I haven't eaten breakfast for years.
I also eat rice, potatoes, pasta, bread, cakes, chocolate, biscuits but not all at once, have them in moderation and have no issue with rice, bread, biscuits, potatoes. Cakes and chocolate can make me crave more and pasta can be high calorie. When I was younger could eat loads of that though without putting on weight as was very active.