Basketball star Shaquille O’Neal has always been a larger-than-life figure, physically imposing but also a huge personality. Yet he’s never been able to translate that into a career off the court. The movies "Steel” and “Kazaam” bombed. They did so by trying to turn O’Neal into an actor, and something other than who he is.

ABC’s “Shaq’s Big Challenge,” doesn’t make that mistake. It lets Shaq be Shaq, the likable giant we know from interviews and sports highlights, without lines to memorize.

Smart move. O’Neal acquits himself quite well, even better than one might expect.

In “Challenge,” premiering tonight at 9, O’Neal’s task is to help six obese children get healthy, but it quickly becomes clear that these kids will require a lot more than positive words.

As he gets to know the kids and their families, he realizes the enormity of the task before him. The kids’ lives are literally at stake. He and his support staff of physicians and trainers must get them and their entire families to take their health seriously.

What separates "Challenge" from other weight-loss series like “The Biggest Loser” and “Celebrity Fit Club” is that it’s not focused on which kid loses the most weight but rather on the dynamics that have gotten the kids where they are and how to change them.

That seriousness of purpose, O’Neal’s enthusiasm and a complicated but sympathetic group of kids make “Challenge” a television rarity: an entertaining, informative and even inspirational series that mostly avoids cheesiness.

As the show opens, O’Neal is going to the kids’ homes to meet them and their parents for the first time. We meet James, something of a goofball, Chris, who loves baseball, then Ariel, the optimist among the lot, Kevin, the competitive one, Kit, who is shy, and Walter, who’s obsessed with video games. All are medically obese.

The kids enter a six-month program that stresses diet and exercise, working with O’Neal’s team, which include his own physician/trainer, Dr. Carlan Colker, trainer Tarik Tyler, as well as a child obesity expert and a nutritionist.

The show is sensitive yet clear-eyed in showing the dysfunction in each child’s home. Chris’s father, a Cuban-American, admits that in their community being skinny means you’re not doing well financially.

James’s single mom, struggling just to get meals on the table, concedes that she depends on fast food too often because it’s easy. Kit’s parents are hugely overprotective of their only child. They express their love with food.

All the kids acknowledge being teased about their weight, which reinforces their bad habits.

O’Neal, with his open, easygoing demeanor, draws the kids out, getting them to share their feelings. He knows instinctively when to turn on the charm and when to rein it in and just listen, as he does when one young boy discusses having considered suicide.

When the kids fib about their workouts and diets, Dr. Colker calls a meeting with the families and starkly describes the health consequences of cheating.

Even as the children, some crying, admit their lies, O’Neal walks among them, whispering encouraging words. And as much as he may want these kids to become hardbodies, he’s a bit of a softie when it comes to how he treats them. He feels for them.

But what ultimately comes across is O’Neal’s deep sense of purpose.

At one point, Kit is taken to the hospital. She’s suffering from an anxiety attack. O’Neal says something as obvious as it is stunning to hear on TV. He’s talking to his staff. If something bad happens to these kids, he reminds them, "It’s my ass on the line.”

O’Neal is right. He’s taken responsibility for the lives of others, people who cannot fend for themselves, and he’s owning up to that responsibility. It’s refreshing, as this honest and well-intentioned show is refreshing.