As a parent, I’m not alone. At least two families I know have banned Fortnite Battle Royale—the supremely popular video game—from all devices in their house. Yet the basketball court and baseball field at the school near our house remain empty most of the time.

In my house, we severely limit Fortnite consumption. As our kids slip further into a world of screens and leave behind the monkey bars, aimless bike rides, and kickball games, there is an inevitable tradeoff: fitness and life in the real world, or Fortnite.

If you haven’t heard, Fortnite has snagged more than 125 million players in less than a year, mostly kids under the age of 18. Many play for 10 or even 20 hours per week. Tens of millions watch Fortnite game livestreams on Twitch and YouTube. Athletes, musicians, and other cultural icons have adopted the game and its campy dance moves, called “emotes.” And the game is set to launch its fifth season in mid-July, which has sent the gaming world into a frenzy.

The media is awash in stories of parents enrolling their children in Fortnite therapy sessions and temper tantrums by youths asked to curtail their Fortnite consumption. In reality, Fortnite is not that different from past youth-centric cultural crazes, from Minecraft to Donkey Kong to Atari to pinball machines. What’s new is its ubiquity, portability, and the duration of time spent on the game. Unlike at any time in the past, roughly 95% of U.S. teenagers have a smartphone or regular access to one, according to the Pew Research Center.

The problem is not confined to Fortnite. Tech companies design their products—like smartphones and social media networks—to appeal to and addict us, a combination of Las Vegas slot machines and digital oxycontin. Naturally, kids—whose minds are even more susceptible to these entreaties than grownups are—fall easily into these traps.

Yes, I’m another old person whining about “those kids today.” But we can’t avoid reality: Kids in this country and the rest of the developed world are becoming less and less fit. Research by Gavin Sandercock, an academic who studies fitness and strength in children, shows that English children’s fitness dropped drastically between 1998 and 2014, with the rate of decline accelerating between 2008 and 2014. A study of children and teenagers in Norway using accelerometers to measure actual physical activity found a marked and steady decline in activity in cohorts measured in 2006 and 2012.

This is a big problem. Fitness is a key holistic element of well-being, strongly correlated with positive outcomes such as success in school, better sleep behaviors, and reduced stress. When we move more, we are happier and healthier.

Fortnite is not going to drive the solution. The company behind the game rakes in over $300 million per month selling skins, pickaxes, and other digital enhancements to help players compete more or simply look cool. Even with tech companies increasingly paying lip service to mindful consumption and moderation, they will never support the best solution for users.

Tackling this problem needs to start at home. Parents and caregivers should restrict Fortnite—perhaps allowing only 30 minutes a day, one or two days a week, or even eliminating its use entirely if the situation calls for it. Parents need to understand that Fortnite is a social activity and that in moderation, it’s actually healthy and helpful to teens trying to assimilate. But vigilance is key in ensuring that its use doesn’t tip over into an unhealthy realm.

Electronic games are not necessarily bad hobbies for children. But if they supplant all other forms of play, then we all end up less happy—even if we have a really cool skin on Fortnite.

Alex Salkever is a regular contributor to Fortune and a technology executive. His new book, Your Happiness Was Hacked: Why Tech Is Winning the Battle to Control Your Brain—and How to Fight Back, was published on June 26.