THERE is good news in the fight against obesity: Rates are finally falling in young children. The bad news? They’re continuing to rise to new heights in adults.

The decline in childhood obesity rates is one achievement within a larger failure. By focusing so much attention on the young, in the hopes that avoiding unhealthy weight gain in childhood would prevent adult obesity, we made the same mistake health advocates made in the battle against smoking 25 years ago. Ultimately, we learned an important lesson in the power of marketing that we should apply today.

The stakes are high. The 38 percent of American adults who are obese are at risk of developing diabetes, heart disease, stroke, cancer and depression. According to a recent study published in JAMA, half of adults have either diabetes or pre-diabetes. A decade ago, when rates were lower, one study estimated that obesity was responsible for some 100,000 excess deaths in a single year. Beyond the human tragedy, obesity and diabetes are top drivers of increases in health care costs, which are gobbling up the finances of governments and families.

The obesity rate in children ages 6 to 11, after big increases, has now flatlined, at 18 percent, and the rate in children ages 2 to 5 has fallen below 10 percent for the first time since the 1980s.