Americans argue about the Affordable Care Act and whether it will, as promised, help to control the costs of health care, but here’s something everyone can agree upon: Reducing the rates of childhood obesity, which has reached epidemic proportions in this country, will help to accomplish that goal. And here is some good news: That urgent task is under way.

A new report from the Centers for Disease Control and Prevention shows a 43 percent drop in the obesity rate for young children over the past decade. With that, children are vastly more likely to grow into healthy adults and avoid the personal and social costs of potentially fatal conditions including heart disease, diabetes and even some cancers.

Childhood obesity was identified as a crisis in this country years ago, and there’s no reason to wonder why it happened. Like too many adults, children are often sedentary, and consume far too much processed food and beverages – products that are loaded with sugar, salt and chemicals that few people know how to pronounce. The problem of American obesity, in children and adults, has been a slow-motion train wreck that has serious consequences.

Not only are obese children more likely to become obese adults, with all the accompanying health risks, but the rates of obesity have begun to threaten the nation’s security. Two former chairmen of the Joint Chiefs of Staff – retired Army Gen. John M. Shalikashvili and retired Army Gen. Hugh Shelton – raised the issue in 2010, writing in the Washington Post that in 2005, more than one-quarter of all Americans between 17 and 24 were too fat to serve in the military.

That’s why this is an issue that demands attention from all quarters, from families around kitchen tables to teachers to the White House, where first lady Michelle Obama has made childhood obesity her cause. The efforts seem to be paying off, though exactly how much is uncertain.

For example, the obesity rates for older children remained unchanged. And, looking at adults, the rates for women over 60 rose to 35.4 percent from 31 percent.

Speaking to USA Today, David Ludwig of Boston Children’s Hospital observed that, despite the CDC’s report, obesity “remains at historic highs.” He has warned that this generation of children could be the first in history to live shorter, less-healthy lives than their parents. The decline in childhood obesity rates, he said, was only an “encouraging preliminary finding.”

That sounds right. Fully taming this beast will take years, if not decades, and will require parents to learn which foods are healthy for their children and which are not. It will require children and adults to do more in their spare time besides texting or watching movies.

Moving is the key: regular exercise and wise eating habits form the pathway to long and healthy lives, and to reducing the costs of health care, which are driven in large part by the kinds of chronic diseases that obesity produces.

So, it’s a start. There is a lot more that must be done, but at least there are clear signs of progress. We dare not let up.