He was only in middle school when it started. The sting and the shame of the insults wounded him, but by the time he was a high school senior, Jared Sullinger had become immune, an expert at repressing the urge to respond.

"Hey Sullinger, you're a fat ass!"

"Hey Sullinger, get in shape!"

"Hey Sullinger, have another Big Mac!"

The validation came in the form of his exceptional basketball skills: the soft hands, the remarkable body control, the superb ability to track rebounds. Sullinger led Northland (Ohio) High School to a No. 1 ranking nationally and was the co-MVP of the McDonald's High School All-America game with Harrison Barnes.

He was a two-year All-American at Ohio State and a projected lottery pick. His basketball career was soaring and Sullinger convinced himself his size was an asset.

He declared his intentions to go pro, but pre-draft reports detected back trouble, which many NBA general managers felt was directly related to his weight. He fell to No. 21, was taken by the Celtics and had a promising rookie season cut short by surgery to repair a lumbar disk.

"Obviously, we knew when we drafted him that weight was an issue,'' Celtics president of basketball operations Danny Ainge said.

Sullinger got up to 300 pounds this season and hopes to get down to 260 by training camp in the fall. AP Photo/Elise Amendola

The Celtics asked him to report to training camp this past October at 260-265 pounds, but instead he showed up 20 pounds heavier and gained even more weight as the season progressed.

In spite of the added bulk, Sullinger posted career-high numbers -- 14.1 points, 8.1 rebounds, 2.4 assists. The results were at odds with the growing problem of his expanding physique, something Sullinger didn't fully recognize until he was diagnosed with a stress fracture in his left foot that ended his season.

It was then the Celtics sat him down and had Sullinger watch the footage of him lumbering up the floor and taking plays off to conserve his wind. His lack of conditioning was unacceptable, and if that didn't change, Ainge warned him, his career with the Celtics could be over.

This was no heckler poking fun at his gut. This was his boss, the man who dictated Sullinger's future, who announced publicly that his power forward was the only player on the Celtics not to meet his conditioning requirements.

"He's not up to the standards he wants and it's not up to the standards we think are in his best interests for the long-term health of his career,'' Ainge said at the time.

As Sullinger retreated to the sidelines, the Celtics experienced a resurgence without him and are in the hunt for the eighth playoff spot while he (literally) treads water in a pool in Waltham, Massachusetts, wondering what his future holds.

"It's hard to watch,'' Sullinger admitted. "I want to be part of it.''

The Celtics already picked up their team option on Sullinger for next season, but he will become a restricted free agent in 2016. Boston wants to see results before it commits to a long-term deal.

Ainge said he has "great interest" in re-signing Sullinger, but he will likely be subjected to a weight clause in his contract, much like Glen Davis had during his tenure in Boston.

"I'm perfectly fine with that,'' said Sullinger, in an interview with ESPNBoston.com on Sunday night. "It's not that I need it. It's the simple fact that I know what kind of person I am, and I would never get back to the weight I was [this season].''

"People say, 'Hire a nutritionist,' but it's not that simple. What people don't understand is after a game, you get hungry. I stay up late, I'm not falling asleep and I want to eat. The hardest calories to burn off are those late-night calories."

Ainge said he wants to believe Sullinger has gotten the message and will lose the weight.

"I think he understands,'' Ainge said. "The question is, Can he do it?''

Sullinger is out of his walking boot and looks visibly slimmer. He claims to have lost "10 or 15 pounds" from riding the exercise bike and committing to a daily workout regimen in the pool.

"My conditioning has been the best it's been all season because of the swimming,'' Sullinger said. "I don't really like it because it's hard, but I feel myself getting faster.''

Under the watchful eye of strength and conditioning coach Bryan Doo and his staff, Sullinger said his first timed lap was 2 minutes, 34 seconds.

"But I've got that down to 1:45 now,'' he said. "I've turned it into a mental competition for myself.''

At the time of the diagnosis of his stress fracture, Sullinger claimed it was "God's plan" and resisted connecting his bulky frame to his injury woes. Since then, he's had time to ponder his situation and acknowledges his lack of conditioning has contributed to him missing 73 of the past 246 games. It is, the Celtics say, a positive step toward taking ownership of his situation.

There are scores of NBA players whose careers were thwarted because of weight issues, among them former Phoenix Suns center Oliver Miller, who played with and was later coached by Ainge in Phoenix. Miller, known as "Big O" because of his size, was a gifted big man who had the skills to be an All-Star center but ballooned to more than 300 pounds and became a journeyman instead.

"Danny told me about him,'' Sullinger said. "I don't want to be one of those guys. I know this could hurt my NBA career. If I [don't lose the weight], I'm playing eight to nine years instead of 10 to 15 years. I can't let that happen.''

Sullinger said he's been battling his weight since he was a young boy. He marvels at teammates whose metabolism enables them to eat as much as they want without ramifications -- players Shaquille O'Neal, who also struggled with his weight, used to call "salad eaters.''

"Do you think I want to be like this? I don't,'' Sullinger said. "My genetics aren't the same as your genetics. Some people can drop 10 pounds in a week. Some can drop 10 pounds in three weeks. My body doesn't work like that.

"But that doesn't matter now, because I've got to figure out a way to do this. It's going to be hard -- it has always been hard -- but I have to take extra care. At the same time, there are obstacles that still occur.''

Sullinger, whose season ended early due to a stress fracture in his left foot, has lost "10 or 15 pounds" since starting a daily workout regimen while rehabbing. AP Photo/Elise Amendola

Sullinger said his most challenging moments were after games when the team put out a postgame spread in the locker room. He knew he was expected to abstain from piling helpings on his plate, but even if he managed to avoid eating with his teammates, he often found himself satisfying his cravings once he got home.

"People say, 'Hire a nutritionist,' but it's not that simple,'' he explained. "What people don't understand is after a game, you get hungry. I stay up late, I'm not falling asleep and I want to eat. The hardest calories to burn off are those late-night calories.

"And that's what has been getting me this year. I have to work 10 times, 30 times as hard to keep off those extra 400 calories.

"Even though the stuff [in the locker room] is good stuff, healthy stuff, my body doesn't react to it the way an Avery Bradley or a James Young does.''

While Ainge and the strength and conditioning staff are sympathetic to Sullinger's plight, they've made it clear they aren't interested in more talk, only actions.

"They told me, 'You got to find a way,' '' Sullinger said, "so that's what I'm doing. I'm trying to find a way.''

Sullinger has not been cleared to resume basketball activity, but he has graduated from walking to some light running. He once held out hope he might be able to re-join the team this season, but Ainge and the medical staff have ruled that out.

So he hops in the pool, rides the bike, then drinks as much water as he can to curb an appetite that seems insatiable to him.

"I know what people think,'' Sullinger said. "They think a snack for me is a sandwich or a couple of burgers. It isn't. It's a cup of fruit. I'm trying.''

He looks to his family, many of whom have also struggled with their weight, for support.

Jared's father, Satch, tipped the scales at 390 pounds two years ago but came to the realization he was compromising his health. He had whittled away 50 pounds when Sullinger's grandmother passed away last summer. She was obese and suffered from diabetes, and Jared believes it was the wake-up call that Satch needed.

"My dad has lost about 75 pounds,'' Sullinger said. "When my grandmother passed, he was at about 340, but her death pushed him to a whole new level.

"I think her health issues struck him. It made him say, 'I don't want to go down this road.' He was already on medication and the doctors told him if he could get under 300 pounds he could get off it, so that was his motivation.''

Satch is down to 270 pounds -- 15 pounds lighter than his 23-year old son.

Sullinger said his goal is to get down to 260 pounds by training camp next fall. That is five pounds below the weight he carried when the Celtics drafted him.

The taunts have not subsided since he graduated to the NBA; in fact, they have only gotten more creative. Sullinger insists he's long past letting them affect him.

More on the Celtics Keep on top of the Green throughout the season with ESPNBoston.com's Chris Forsberg. Blog »

"They just yell stuff to irk my nerves,'' Sullinger said. "It doesn't bother me because I know the hard work I've put in to get here. They yell the things they are yelling, but I can take that person and put him in the same workout I'm in, and I can be 20, 30 pounds overweight and they can be the size they've always been, and I'm still going to get through faster than they will because I know what it takes to be an NBA basketball player.''

What Ainge wonders aloud is if Jared Sullinger understands what it will take to remain a productive NBA player on the Celtics roster.

"We absolutely know he can play,'' Ainge said. "We're trying to help him get through this.

"He should not be playing with this injury. I hope he can get there.''

The Celtics believe Sullinger weighed in excess of 300 pounds this season. The power forward balks at that number

"The heaviest I got was 298,'' he insisted.

He is told his team begs to differ.

"I didn't get over 300,'' Sullinger said. "I was close, but I didn't.''

He paused for a moment.

"Well, maybe one day I was ...'' he offered.

That was one day too many; now, it is one day at a time. Sullinger's career depends on laps and fruit cups and late-night resolve.

"The biggest thing is motivation,'' he said. "I have to make sure, with this foot injury, that it doesn't ever happen again.

"I've got to get in the best shape possible. Not just for the Celtics, or basketball.

"I have to do this for myself."