They are the kids who get picked last for the game, if they get chosen at all. They are the slow runners, the “easy outs,” the ones who eventually just don’t bother to show up.

“It’s harsh, but these are the fat kids,” said Mary Williams. “They are overweight and then they start to feel so bad about it that they give up playing with friends and go inside, where they gain even more.

“They lose their childhoods this way,” she said.

Williams, an athletic trainer, is working to help children who are caught in the obesity epidemic in a state where one in every four children is overweight or obese. But her goal isn’t just to help them lose weight; it’s to use sports to teach them lifelong ways to stay fit.

She has a group of 10 girls ages 8-16, who come to her Wayne, N.J., gym twice a week to play sports away from the harsh reality of their local playgrounds. They begin with the fundamental skills of soccer, basketball and softball, then play each other in scrimmages. They also play kickball and go biking and hiking. They recently tried indoor rock climbing. Over the winter, they went skiing.

“It’s amazing to see how these girls brighten up when they realize they can do something they see kids doing all the time in their neighborhoods,” Williams said. “You see them laughing and having fun. Getting fit.”

And losing weight. The girls usually have begun a weight loss plan when they are referred to Williams by their pediatricians or nutritionists. Williams loves watching their transformations. Most important, she loves giving them a reason to move.

“Kids are not going to stick with a regular gym atmosphere,” she said. “... They are kids, and kids play.”

Williams’ sessions have turned 12-year-old Marisca into something of a soccer nut. Marisca, a Passaic, N.J., resident, was 40 pounds overweight when she attended her first class two years ago. “Back then, I couldn’t run 10 steps without heaving,” she said.

Now that she’s slimmer and fitter, she plans to try out for a soccer team. She practices every day in her back yard and has even started playing with other kids on her block. “I don’t like to sit around anymore,” she said.

The sessions have motivated Emily, a 14-year-old Englewood, N.J., resident, to set her sights on shot put when she starts high school. “I’m really strong,” she said. “They say it’s about the power in your legs, and I have power those skinny girls don’t have.”

The thing Emily and Marisca said they have most enjoyed about the sessions with Williams is that because the group is filled with girls like them, they aren’t afraid to try a sport. “Nobody is staring at you and thinking you are too fat to play,” Marsica said.

In fact, they cheer one another on. With their help Ellie, a 13-year-old Wayne resident, has discovered she is a powerful hitter. She hopes to play on a softball team next spring.