In many ways, the health outlook for adults in America has brightened considerably since the 1960s. For example, the percentage of smokers has decreased during the past 50 years. Meanwhile, access to various cancer screening examinations has expanded. And medical technologies and treatments have become increasingly sophisticated.

But another key component of human health – personal body weight – has grown much worse for wear. In 1960, about 13 percent of adults 20 and older in the U.S. were classified as obese. Today, the ranks of obese adults have grown to 34 percent.

The culprits are varied. Larger meal portions and higher consumption of cheap, tasty and readily available processed carbohydrates, fast foods and “junk” foods add up to more calories. Meanwhile, electronic devices, computer games and ever-growing television screens contribute to more sedentary lifestyles. Biological and environmental factors can also play a role.