UCLA’s Joshua Smith has been a big man on campus since he was 5

The kindergarteners needed saving from Joshua Smith. The playground monitor was sure of it.

Here was Smith, a 5-footer, playing with children a fraction of his size. It seemed like a disaster in the making.

So the monitor intervened, shuffling the towering boy over to a group of older kids thought to be his peers.

“The monitor made assumptions based on his size that he had to be older than 5,” said Tracey Smith, Joshua’s mother.

It’s dangerous to make any presumptions about the boy who grew … and grew … and grew to become UCLA’s starting center as a freshman.

Now Smith is 18 years old, is 6 feet 10 and, judging by the snug fit of his XXXL uniform, heavier than his listed weight of 305 pounds. Yet his father is 6-2 and his mother 5-4.

Smith dwarfs both his older and younger brothers. Yet he was the smallest of the trio at birth — at seven pounds, 11 ounces.

Doctors wondered if Smith might have an overactive pituitary gland, but Tracey Smith said her son never was diagnosed with any abnormality.

“I just kind of sprouted out of nowhere,” he said. “I just kept growing and just kept eating what my mom was cooking. I dedicate my height to my mom’s cooking.”

The Bruins must devote a hearty chunk of their success during a bounce-back season to Smith. He has provided an interior presence UCLA lacked in recent years, clogging the lane for easy baskets and a Pacific 10 Conference-leading 55 offensive rebounds.

Size isn’t the only thing Smith has to offer. He possesses soft hands, a deft passing touch and leads the Bruins with 10 charges taken and 62 second-chance points.

“It’s so hard to box him out and get around him on the post, and he’s much more nimble than people might think he is,” said Washington Coach Lorenzo Romar, who had hoped to slip a Huskies jersey on Smith, a native of Kent, Wash. “He’s got that big body, but he still elevates and gets off the floor on those dunks.

“You’re not seeing anything compared to what you’re going to see when he gets in great shape.”

Smith already has shaved at least one X off his jersey size, dropping about 50 pounds since he arrived in Westwood last summer. He continues to slim down, spurning the gumbo and peach cobbler dishes his mother made over the holidays in favor of lean chicken and rice.

Not that his younger sibling made things any easier for him.

“My little brother Jeremy took advantage of this opportunity and was eating in front of me,” Smith said of the 16-year-old. “ ‘Hey, Josh, try this peach cobbler. … Oh, wait, you can’t have it.’ ”

The elder brother got his revenge by taking his shirt off, revealing a more svelte physique. Before he returned to Westwood, Smith also delivered a little love tap he described as “a goodbye punch.”

Despite his size, the easygoing Smith has never acted like a big shot. Even as a 6-7 high school freshman, he managed to blend in with his classmates.

“He was very outgoing, almost friends with everyone, and kids liked that because he never tried to walk around campus as if he was ‘it,’ ” said Michael Annelids, Smith’s coach at Covington (Wash.) Kentwood High.

Smith grew about 1½ inches each year until reaching 6-10 at the end of his junior season. His mom scoured stores to find shoes that would fit his feet, currently size 19.

Tracey Smith had hoped her son would pick the college within walking distance. Though she grew up in Southern California and attended Reseda High, Tracey wanted Joshua to play for Washington, her alma mater. He seriously considered it.

“I always thought of staying home and playing for U-Dub,” Smith said. “It’s 15 minutes from my house, my mom and dad could go to the games and I could play against guys I’ve played with [growing up] and just be a hometown kid.”

All that was nothing, it turned out, compared to the allure of powder blue. Smith had become a UCLA fan since compiling an eighth-grade report on Bruins Coach John Wooden. His affinity for the school was strengthened when he visited Westwood and met his prospective teammates.

“I just felt I couldn’t pass up the opportunity,” Smith said.

He was in the Bruins’ starting lineup for his first college game, but staying on the floor proved to be a problem. Smith committed four fouls in each of his first five games and averaged only 16 minutes. It started to wear on him.

After watching his son slog through a foul-plagued game on TV, Josh Smith Sr. told the freshman he looked as though he had lost his best friend.

“The foul trouble was kind of consuming him,” said Josh Sr., a former shooting guard and small forward at McMurry University in Abilene, Texas.

Then came a breakthrough. Smith scored 17 points and snagged 13 rebounds against Kansas and followed that two games later with a 19-point, 12-rebound effort against Cal Poly San Luis Obispo. He is averaging 10 points and 6.9 rebounds in 19.8 minutes per game and has fouled out only once.

“He is a hard matchup,” UCLA Coach Ben Howland said. “He’s got to get better for us in transition defense, and just defense period, because people that can space him out away from the basket, that’s where he gets hurt the most. But I’m really, really excited about Josh.”

There’s plenty to like about a player who pushes around opposing big men as if they were nothing more than giant marshmallows.

“He can do whatever he wants to inside,” Bruins sophomore forward Brendan Lane said. “I mean, he’s just so big and so strong and nobody can stop him.”

Nobody, that is, except the playground monitor.

ben.bolch@latimes.com