Obesity is a serious health problem in the United States and increasingly around the world. Costs and associated diseases continue to increase. Recent studies into the causes of obesity indicate that the problem is more complex, and may have less to do with “willpower” and other such issues, than previously thought. Many obesity experts hope this research will help physicians and others rethink the way they understand and treat the problem. Skeptics, however, continue to blame inactivity and overeating for obesity. While the World Health Organization (WHO) and others call for a reduction in sugar consumption to combat obesity, the food industry says it is being unfairly targeted.

Healthy school lunches — like whole-grain pasta salad with plenty of vegetables — may be one way to help reduce childhood obesity. But critics of the federal Healthy, Hunger-Free Kids Act call that law’s nutritional requirements government overreach. (Getty Images/Kansas City Star/MCT/Tammy Ljungblad)

The planet’s population is getting fatter. Once a problem largely confined to high-income regions, overweight and obesity are on the rise in low- and middle-income countries. According to the World Health Organization (WHO), obesity has more than doubled worldwide since 1980. In 2014 more than 1.9 billion adults (39 percent of Earth’s adult population) were overweight. That includes 600 million who were obese. 1

Among children, overweight and obesity are increasing more than 30 percent faster in lower-and middle-income countries than in developed countries. In 2013, 42 million children under the age of 5 worldwide were overweight or obese. 2