When the 17-year-old came to us for help, he told us he weighed 400 pounds.

He was wrong. That was just the maximum weight on the scale at his doctor’s office. A quick trip to a hospital told us he weighed 521. Once we knew the true size of his problem, we got to work.

I became involved with the obesity issue after watching my 550-pound father, Big Louie, die of a stroke. I formed a nonprofit group, Louie’s Kids, to work with children ages 10 to 18 to help make sure they didn’t go down the road my dad painfully traveled. When I started out in 2001, we were working with teenagers whose weights began with the number 1, or in the worst cases 2. Today we’re not even shocked to see numbers that start with 3 or 4.

But kids don’t have to be that heavy to suffer the problems that come with obesity. Many of those we work with are 20, 30 or maybe 50 pounds overweight — and they have to deal with the stereotypes that they are lazy, unintelligent, unable to keep up with other children. They come to us because they want to turn their lives around.

We’ve helped hundreds of these kids accomplish just that. Most of those who succeed in losing weight and keeping it off have some things in common.

First, they have caring parents who make a commitment to eat dinner together. When children sit down to have meals with their family, it changes their relationship with food; we have seen it work time and again. Second, they learn to eat real food, cooked by a real person, not something that comes in a cardboard box. Third, no sweet drinks. Most overweight kids ingest a disproportionate amount of their calories in sweetened beverages, which feed the need for more sugar and wreck their metabolism.

Finally, successful children find a physical activity they love and do a lot of it. So we offer after-school programs for students and hold family workouts in parks; we buy kids bicycles or memberships at the YMCA or other rec centers. We try to expose them to a little bit of everything. Maybe they’ll fall in love with Tae Bo or kettlebells or hip-hop dance classes or yoga. We give every kid a pedometer and say the day is not done until it clocks at least 10,000 steps.

To encourage better eating habits, we teach families how to shop at the grocery store. We show them which aisles to stay out of and which will give them the healthiest bang for their buck.

We also connect some kids with cognitive behavioral therapists — and if we can’t do so in person, we do so via Skype. Often overweight children are dealing with some underlying problem, such as bullying or abuse or the death of a parent. We’ve found that kids are more likely to come to grips with their physical problems once the psychological problems are treated.

Scientists tell us that 80 percent of obese children are likely to become obese adults. Sure, our health-care system can hold these people together — controlling their diabetes, replacing their knees and hips, holding down their blood pressure. And costing taxpayers a fortune.

But I have seen young people escape that destiny. I’m working with a young man who has lost about 70 pounds and is still dropping. He scored 1486 on his SATs and is off to college. It looks as though his future will be bright. He has proved the stereotype wrong: He’s smart, capable and ready to empower himself.

And there’s the fifth-grade girl who was about 30 pounds overweight. She would not speak unless spoken to, and habitually looked down at the ground. We put her into group therapy to try to change her behavior around food, and gave her coaching in nutrition and physical fitness. She has lost about 20 pounds, but the biggest change is her sense of self worth. Her principal told us he was amazed to see her raising her hand in class, confidently asking questions. She smiles and greets other kids.

Our message to parents: Intervene now if you think your son or daughter is eating the wrong things. Get your child up and moving. I have seen how hard it is to go through life weighing more than your body can bear. I’ve also seen that it doesn’t have to be that way.

Louis H. Yuhasz is the founder and chief executive of Louie’s Kids, based in Charleston, S.C.

23.5 million

Number of children and adolescents in the United States who are overweight or obese, which is nearly 1 in 3.