In the 1950s — before the invention of BMI (Body Mass Index) — Jean Mayer and others did a study of obesity at a factory in India. They divided workers by how much exertion their job required. Almost everyone, even desk clerks, was thin, with the exception of the most sedentary. It appeared that walking one hour per day (to and from work) was enough to get almost all the weight loss possible with exercise. Doing more had greatly diminished returns. A study with rats suggested the same thing. Bottom line: If you’re sedentary, you can easily lose weight via exercise, which can be as simple as walking to work. If not, it’s hard.
This month GOOD has a kind of update of that ancient study — a scatterplot, each point a different country, that shows percentage of obesity and fraction of commutes that are active (bike or walk). It supports what Mayer and others found — that how you get to work makes a difference. If you fitted a line to the data it would have a negative slope (more obesity, less active commutes). America has the most obesity and relatively few active commutes; Switzerland has the most active commutes and relatively little obesity. The graph also suggests that other factors matter a lot. Although Australia has less active commutes than America, it also has less obesity.