Mason Finley lost more than 100 pounds in his quest to make the U.S. Olympic team. (Andy Lyons/Getty Images)

Before he had locked up a spot on the U.S. Olympic team, before the scale told him he weighed 437 pounds, before nagging injuries almost forced him to abandon his dream, Mason Finley was a young boy rifling through his father’s closet. He unearthed some heavy discs and took them to his father.

“I asked him, ‘What the heck are these?’ ” Finley recalled. “I had never seen anything like it. I thought it was cool.”

Jared Finley had thrown the discus in high school and college. He wanted to give his son a discus to throw, so he taped together a pair of Frisbees and filled the inside with sand. The two spent their weekends together, hurling the makeshift disc as far as possible until the grade-school Finley finally graduated to the real thing.

“I kind of equate it to a father and son going fishing,” says Finley, now 25. “It was our bonding time, an interest we shared.”

Finley kept throwing, ultimately earning his way to the Rio Games, where he will compete in the time-honored Olympic discus throw. But to grow as an athlete, Finley first needed to shrink as a person.

Discus is a sport that rewards strength, and its competitors are among the Olympic giants, a combination of brawn and athleticism. But even by their bulky standards, Finley had become much too big.

He entered college at 340 pounds, much of it muscle that filled his 6-foot-8-inch frame proportionally. He spent three years at the University of Kansas before transferring to Wyoming, his father’s alma mater. He divided his time among practice, classrooms and the training table, where food was never in short supply.

“I’m an eater, man,” he says. “There’s no way around it. I like to eat food.”

By his junior year he hit 437 pounds, nearly 100 pounds heavier than he was as a promising high school thrower. He was still physically strong and still throwing great distances, but he also knew that getting bigger was different than getting better — and an Olympic throw away from being fit and healthy.

“I remember times I’d be walking around and my ankles would just pop,” he said, “every other step or so.”

Lifting weights became more difficult. He kept hurting his back and suffered from nerve damage and two herniated discs. In the throwing circle, he felt slow and stiff.

Here's what four Olympic athletes eat to fuel their training. (Daron Taylor,Jayne Orenstein,Dani Johnson/The Washington Post)

“It was really frustrating. I was very powerful still, but I never felt I was at the top of my game,” he said.

He didn’t look like the twirling, nimble throwers he grew up watching. Growing up in Colorado, he was in the seventh grade when he watched the 2004 Athens Games and caught the Olympic bug. He saw giant men flicking the disc into the sky like it was nothing. Shortly thereafter, his mother arranged for Finley to shadow Casey Malone, the top American finisher at the Athens Games, for “career day.” Malone was coaching at the University of Colorado in Boulder, not far from the family’s home near Buena Vista .

“That’s where it really hit me,” Finley said.

His father helped him tinker with his technique, working on footwork and balance. Finley set a national record in high school. He dabbled in other sports, but throwing always felt different. It was a pursuit that rewarded his size and offered tangible, easy-to-measure successes.

“You definitely feel something special happening,” he said. “You feel like all your energy has gone into the disc. . . . It was something I definitely shined in because of my leverage, my strength. It was a really nice fit for me. It’s not like I was breaking any records in the 100-yard dash or the high jump.”

When he reached college, though, he didn’t know when to pull back. Bigger meant better, he figured. More food and more muscle might mean more distance on this throws.

“I just wasn’t educated enough to know what I was putting my body,” Finley said. “I had no idea how many calories I was putting in or that carbs are freaking everywhere. It was silly how little I knew on the subject.”

He really started studying nutrition as his college career wound down, and he realized that to pursue his Olympic dream, he would have to shrink. He began devouring books and articles and in 2014 attended the U.S. Olympic Training Center in Chula Vista, Calif., where the medical staff made clear that his weight had become an impediment.

He tweaked his routines and overhauled his diet. He would eat carbs only before a workout and would focus other meals around healthy calories and fats, usually egg whites and good protein. In the fall he did more cardio exercise, swims and didn’t hit the weights as aggressively. He lost nearly 50 pounds in just a few months, and the lingering aches and pains from college disappeared.

His weight is down to 345, and he feels stronger than ever. He was more flexible in the throwing circle and more powerful with the discus. Finley is able to squat 560 pounds for three reps and bench 460 for two.

“My technique is far better,” he says. “I’m healthy — which was really rare in college — and I’m faster, probably same speed as high school.”

Staying trim and physical is a full-time endeavor, though not a well-paying one. Finley graduated with a theater degree from Wyoming, but chasing the Olympic dream hasn’t left much time for acting. In February he moved back to Lawrence, Kan., which allows him to live rent-free with his mom, Lisa. He works part-time at a GNC and in the fall and winter earned extra money as a bouncer. He has had bit parts in independent films in Lawrence and auditioned last fall for the role of King Triton in a production of “The Little Mermaid.” The rehearsal schedule was too demanding, though, and wouldn’t have left enough time for training, which requires anywhere from three to six hours most days.

Reaching Rio is only the first step. For years, the United States dominated the men’s discus, winning 14 of 19 gold medals through the 1976 Games. But that marked the last U.S. gold, and no American man has medaled in the discus since 1984. No American has reached the final round, in fact, since Malone in 2004.

“You hear some people talk trash about American discus throwing, but I definitely think the team we’re sending and the future of American discus is definitely coming around,” said Tavis Bailey, another American thrower competing at these Olympics. “We’ve got some talent going to Rio.”

Finley feels he can reach the Olympic final and really hopes to throw at least 65 meters — 213 feet 3 inches — which is a magic number of sorts for discus throwers and could lead to invitations to overseas meets and more opportunities.

At the U.S. Olympic track and field trials last month, he threw 66.7 meters — 218-11 — a personal best, in the qualifying round. Competing in rainy conditions, Finley won the trials one day later with a throw that was 10 feet shorter.

“It’s a huge relief, but that throw isn’t going to do very well in Rio,” he said then. “We’ve got to turn on the afterburners.”

For Finley, that means being stronger, throwing farther and competing lighter than he has in years.