Only 20% of American jobs are even mildly strenuous

There has been a marked increase in national obesity in the past forty years, not only in the US but worldwide. You see documentaries from the 1940s-1960s and ordinary people on the street are slim. What is the cause for the rise in obesity? Changed governmental dietary advice, access to fresh food, preferences for carbs, loss of the tradition of family meals, over reliance on fast food? There are lot's of popular theories. Everyone agrees we are more sedentary than in the past but that observation is offered without qualification.

From Working hours: Get a life—or get fat from The Economist.

So why do long hours result in weight gain? Only 20% of American jobs are even mildly strenuous, compared to 50% in 1960. In 1960 a tenth of the American workforce was involved in agriculture, but today it's more like 1%. More time at the desk means less movement. Busy people may have less time to prepare good meals, instead choosing a take-away. (Management consultants, in my experience at least, tend to be rather knowledgeable about fancy restaurants near them that also deliver). They exercise less. And workaholics sleep less: inadequate shut-eye is associated with weight gain.

50% to 20% of people with jobs that are mildly strenuous - that's a pretty big drop.