If you as an individual want to change your weight, you must change your whole life. Likewise, to reduce obesity in modern society, we will have to alter the way society is organized.
Weight gain is driven by two trends: increases in calories consumed and decrease in calories expended. Modern America induces both.
For example: The after-inflation cost of sugary soda has declined by an estimated 48% over the past 20 years. Correspondingly, consumption of sugary soda has soared: Sugary soda is now the single most important source of calories in the American diet.
For example again: The number of Americans who work at physically taxing jobs continues its steady decline. Even those jobs that demand physical labor — manufacturing, for example — are much less grueling than they used to be, as electrically powered machines do the lifting and shifting that used to consume human energy.