This is the most comprehensive review I have read on the topic of obesity.  It’s a 30 min read.   It appears to me that we have become victims of our own economic development and an uncontrolled food industry. The study did not include longitudinal studies on physical activity.    One wonders if rationing as in during the war might be an option?  😀
https://www.bmj.com/content/361/bmj.k2538

Key messages from the paper:

• The balance between calorie intake and calorie expenditure determines body weight and body fat changes
• Different foods influence total energy consumption by modifying appetite, or by affecting energy expenditure, eg through diet induced thermogenesis
• Overweight people generally consume more food energy (calories) than thinner people to maintain their higher body weight.
  •Any diet plan that an individual is able to adhere to will cause weight loss, but different dietary patterns may influence adherence to different degrees in different subgroups
• Weight loss maintenance is a greater challenge than weight loss for many people because it requires adapting to permanently eating less energy despite living with in the same physical, social, cultural, and educational environments in which they developed obesity