Contrary to popular belief, the obesity epidemic has been slowly and steadily building for over 70 years. By looking at BMI changes since 1882, researchers discovered the pandemic’s roots stretch back to at least the 1950s, and likely much earlier.
A constellation of cultural factors are at play.
The inventions that define the post-industrial way of life all play roles in reducing movement and increasing consumption of processed, sugary foods as well as low-cost meat. These include labor saving technological advances, the rise of the fast food industry, snack foods, cars, and computers. (See other causes of obesity here.) Like snowflakes in a blizzard, each of these seemingly benign advances leads to a massive storm of fatness.
Fat people from the past would be considered dainty today.
The biggest people in 1882 weighed a lot less than the biggest people today. White women in the 90th percentile of BMI in 1882, for example, were 128 pounds lighter than women in the 90th percentile today. The rate of change in BMI varied between different races; the difference between black women in the 90th percentile in 1882 and today is a tragic 174 pounds.
BMI may actually be underestimating how many people are overweight and obese.
The body mass index measures body fat based on the weight and height of a person. BMI is deeply flawed when it comes to measuring individual health (short, muscular people qualify as obese, for example), but it is more useful for generalizing about entire populations. But there’s a problem: BMI standards for different heights were widely adopted by the medical community in 1972 (Source) – a time when post-industrial changes were already underway and obesity was already on the march. We may be underestimating how overweight we actually are because we no longer have a good grasp of what the healthy body weights could or should be.