More than one-fifth of preschool children are overweight or obese. That’s 20 percent of kids 5 years old and younger who are already on track for chronic health problems such as cancer, type 2 diabetes and heart disease before their first day of kindergarten.

That’s more than 4 million toddlers already queued up for health issues that will last them a lifetime. And of the heaviest youngsters — those who are obese — more than 160,000 live in Tennessee.

Our state’s and our nation’s obesity epidemic is well-documented, and childhood obesity continues to be an appropriate focus. We are learning more and more how nutrition and exercise at the very earliest stages of life can have a dramatic impact on our bodies as we age.

If the body mass index (or BMI, the ratio of height to weight that is typically used to determine a healthy weight) increases too soon or too rapidly for a young child — as young as 3 years old — research shows that child has a much higher risk of obesity later in life.

In short, too much fat produced too early sets the stage for a battle against obesity that will last a lifetime. Before most kids can add 1 plus 1 and get 2, their bodies are learning that being overweight is a way of life.

To start our children in life along this path is simply unacceptable.

There are plenty of statistics to cite, from economic — nearly $150 billion per year is being spent nationally to treat obesity-related medical conditions — to national security — more than 25 percent of all Americans ages 17-24 are unqualified for military service because they are too heavy. But those statistics shouldn’t be necessary.

Being overweight doesn’t necessarily equate to low self-esteem or an inability to achieve, but we cannot intentionally start toddlers out with a predisposition to type 2 diabetes and cancer and heart disease and expect things to be easier for them.

The next 15 years are going to be hard enough; we don’t need to make things any more difficult.

Solving the problem, however, is more complex; there is no silver bullet. Private- and public-sector leaders all have a critical role to play.

Several mayors from across the country recently pledged to do more for those in early child-care education settings in their cities. Many private-sector companies are helping to curb this epidemic, too. Specifically, a recent commitment from the planet’s largest retailers and food and beverage manufacturers to reduce calories in their products by 1.5 trillion by 2015 is laudable.

Parents, get kids moving

Parents also play a role. That’s why we’re calling on everyone to get our youngest kids more physically active. Whether that’s taking a walk or playing a game, it’s just as important for the 3-year-old in your life as it is for the 33-year-old in your life (or, in my case, older still). Cut out the sugar-sweetened beverages for kids under 5 and look to low-fat or nonfat milk for kids over 2 years old.

Equally, the private sector needs to continue to step up. Parents don’t need more complexity and more costs; they need more answers and easier ways to provide a healthy lifestyle for their kids. We need the private sector to make healthy choices as easy and as economical as possible.

We’re asking private industry to better serve their customers and communities by helping them access healthier products. This allows kids to have healthy childhoods. We can do better.

For a nation that prides itself on opportunity, we owe our youngest and most vulnerable at least that: the pledge to ensure their future is as healthy as possible.

And that means starting right from the beginning.