The problem has its roots in our relationship to food and that some types of food act like a drug. This and some of the physiological factors you mention, L.J.
There has been a lot of ink spilled about the fact that our diets are heavily weighted toward sugars and carbohydrates. Sugar can be a rush and carbs like white bread and pasta are just wonderful (at least to me).
Once I hit my 50s my weight became a struggle. I’ve managed to lose twenty pounds in the last eight months, but it’s been a long slog. I have to watch what I eat constantly. There will never be a time when I’m not, in effect, dieting, unless I really increase the amount I exercise.
People make different choices. Not everyone wants to diet all the time. Given the lifestyle that many of us lead and the food that is readily available, it’s easy to be overweight.