If inactivity is “the real villain” behind obesity, it’s easy to pinpoint the best solution: exercise (“Children are not innocent victims of obesity,” Opinion page, Aug. 11).

According a recent study by the Journal of the American Medical Association, fewer than one in three of our kids meet the minimum activity recommendations – a fact that’s easy to explain. We’ve engineered activity out of our lives.

Even household chores require less effort for this generation, since traditionally manual tasks have been replaced by automated versions (drive-through car washes, riding lawn mowers, etc.). The Cooper Institute in Dallas estimates that little changes like these can decrease energy expenditure by almost 9,000 calories a month – the equivalent of 2.5 pounds of body fat.

Looking at these figures, it’s hard to understand why many obesity campaigns and health policies narrowly target food. The scientific evidence focuses on sedentary lifestyles as the problem behind our growing behinds. Our public health policies should too.