The simple answer for this is that calorie intake is higher than the number of calories burned. But why are people getting fatter? In which countries are people the fattest?
This is the questioned tackle in a working paper by Sara Bleich and colleagues “Why is the Developed World Obese?” Obesity is a serious disease:
Excess body weight is the fifth most important risk factor contributing to the burden of disease in developed countries. Rising body mass index steadily increases the risks of type 2 diabetes, hypertension, cardiovascular disease, and some cancers.
Unsurprisingly, the U.S. has the highest rates of obesity throughout the data collected, but the rate of increase is very similar across all countries. Recent news reports (“Over 20m Chinese suffer diabetes“) even show that developing countries such as China are starting to experience higher rates of diabetes and obesity.
The main cause of increased obesity rates is increased food consumption. This is mostly due to decreasing real food prices over the past century. Another factor is the increased female labor force participation rate. One story to go along with this is that as more women work, families cook less and instead eat out more. If dining out occurs in high calorie restaurants and fast food establishments, calorie intake will increase.
The other facto influencing obesity is decreased activity. The main societal reason for a decrease in physical activity is the decrease in the number of active jobs. As the number of manual labor and manufacturing jobs has dwindled in the later half of the twentieth century, many more people are working at desk jobs where there is little physical activity. Further, increasing urbanization rates over time has also lead to decreased physical activity. Perhaps surprisingly, the number of cars per capita or the internet usage rate has no effect on obesity.
The authors claim that a junk food tax may help to decrease obesity and improve societal health. I am skeptical of this solution. Which foods will be categorized as junk foods? Who will decide this? I would guess there will be much lobbying by large food companies to have their products labeled as non-junk foods. Further, a junk food tax would hit the poor more heavily than the rich.
- Sara Bleich, David Cutler, Christopher Murray, Alyce Adams (2007) “Why is the Developed World Obese” NBER WP #12954.