EARLIER this year, we got what seemed like the first good news on obesity rates: A study in JAMA found that there had been a 43 percent drop in the obesity rates of 2- to 5-year-old children in the last decade. But then, last month, that news was contradicted by researchers at the University of North Carolina who used the same data to find that obesity rates had remained flat after all.

With two-thirds of adults and one-third of kids overweight or obese, it’s hard not to feel discouraged. If current trends continue, by 2030, the incidence of obesity-related conditions like Type 2 diabetes could be 20 times what it is today, costing the American economy up to an additional $580 billion annually.

Are we “losing the war on obesity,” as the New York City mayor, Bill de Blasio, put it, and not doing enough to defeat it? No. In fact, if we compare the fight against obesity to the last public health challenge of similar size — the fight against smoking — it turns out that we are being much more aggressive today.

Research linking smoking to lung cancer began appearing in medical journals as early as the 1920s, but the dangers didn’t reach the popular press until 1952, when Reader’s Digest published “Cancer by the Carton.” Still, smoking rates continued to rise. Between 1940 and 1964, consumption more than doubled to nearly 4,500 cigarettes per adult per year. They were everywhere: Hollywood movies, military rations, the workplace, you name it.