Everything in moderation, sez me.
Stressing over what you eat, and how much you exercise, has got to be as bad for you as NOT eating right, and NOT exercising. Likely worse.
My opinion only. Your mileage may vary.
You’re right. Stress is the key, a very important factor. That’s why not everyone fits neatly into the studies, and the “my fat, smoking, drinking gran was healthy in her 90’s” stories abound.