Childhood obesity has been – and remains – a threat to the nation’s wellbeing. From the costs of lifelong medical care to an inability to staff the military services, the crisis of childhood obesity is a gun waiting to go off.

But, unexpectedly and hopefully, signs of improvement have appeared. The Centers for Disease Control and Prevention reports that at least 18 states have seen declines in obesity for low-income preschoolers. It’s too soon to celebrate, but the news comes as welcome relief. Now we need to find out why it is happening.

Thomas Frieden, director of the CDC, called it a “significant decrease” but also noted that with one of every eight American preschoolers obese, rates remain too high. The rates are even worse among African-American and Hispanic children.

It’s a significant problem, and not just among children. While the CDC notes that a third of U.S. children and teens are obese or overweight, the same is true of more than two-thirds of adults. The consequences can be catastrophic. Among children, the CDC reports, they include:

• Risk factors for cardiovascular disease, such as high cholesterol or high blood pressure.

• A likelihood to have prediabetes, a condition that offers high risk for development of diabetes.

• Increased risk for bone and joint problems, sleep apnea, and social and psychological problems such as stigmatization and poor self-esteem.

Long term, children and adolescents who are obese are likely to be obese as adults and therefore at increased risk for heart disease, type 2 diabetes, stroke, several types of cancer and osteoarthritis. The propensity for adult obesity was identified in obese children as young as 2.

Obesity is also affecting the military. Two former chairmen of the Joint Chiefs of Staff – Retired Army Gen. John M. Shalikashvili and retired Army Gen. Hugh Shelton – sounded the alarm three years ago, noting in the Washington Post that in 2005, more than one-quarter of all Americans between 17 and 24 were too overweight to serve in the military.

That is why the report of broad-based, if modest, improvement is so welcome. The more significant declines were found in Florida, Georgia, Missouri, New Jersey and South Dakota, each of which saw its obesity numbers fall at least 1 percentage point. New York was among the other states showing improvements.

What is important now is for researchers to understand the reasons for this decline, with a goal of both broadening and hastening its influence.

There will have to be many approaches to this issue. Children in low-income families tend to be heavier, possibly because they eat more processed foods. Exercise also needs to be part of the solution, and efforts are under way in Western New York to provide those opportunities.

Still, it is worth at least a momentary sigh of relief to note that, perhaps, the trend is changing. Now we have to keep it moving in the right direction.