Sun Yang, who resumed training on Wednesday after being suspended for a month, gained 5 kg while he was out of the pool. Qin Lang / Xinhua

After being suspended from training for more than a month for driving without a license in November, swimmer Sun Yang looked stockier than usual when he returned to the pool at a high-altitude camp in Yunnan province on Thursday.

"Yes, I gained some weight but I'll get back into competition shape soon," the Olympic champion said in a CCTV interview.

His public image and professional reputation, which were badly tarnished by the scandal, may take longer to recover, and Sun has to learn from his eventful 2013, experts said.

"There's no doubt he can regain his athletic form, given his talent and tough training regimen, but to get beyond the negative social image will take a long time," said Zhang Qing, founder and CEO of sports consulting company Key-Sports.

On Nov 3, Sun was caught driving without a license after a car accident in Hangzhou, Zhejiang province. He was placed in detention for seven days. The National Swimming Administrative Center later indefinitely suspended him from training, racing or participating in commercial activities, citing his violation of team rules. The training suspension was lifted on Wednesday.

Earlier this year, Sun created controversy when he sought to replace his mentor of 10 years, Zhu Zhigen, over differences in balancing romance and career.

Sun said in the CCTV interview that he has grown up and will work to discipline himself and correct his faults, but Zhang said that is not enough.

"He should officially apologize to the public and try to realize the impact he could have on followers as a celebrity," Zhang said.

Hong Jianping, a sports public relations researcher at Beijing Sport University, urged other sports figures to learn from Sun's experience.

Due to their lack of education and social experience, sports celebrities in China sometimes have their reputations damaged after getting involved in scandals.

Both Hong and Zhang suggested teaching athletes more about legal affairs and public relation skills.

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