Red Sox third baseman Pablo Sandoval is on the disabled list for a shoulder injury but that is the least of his health issues insiders now say.

According to Sandoval’s ex-trainer, the free-agent bust is so prone to overeating that he needs a food babysitter. The trainer isn’t alone, either, as insiders say when Sandoval was with the Giants the team banned him from using room service during away games.

The trainer, Ethan Banning, the owner of Triple Threat Performance, revealed to the Boston Herald that twice he helped Sandoval shed excess pounds during two consecutive off-season winter breaks.

In fact, the trainer says he and the player — who is only in the second year of his five-year, $95 million contract — worked together far in advance of an upcoming season for fear that if team management saw him “looking like Santa” after the holiday break his salary might be in jeopardy.

“I would go pick him up at a random location, drive him to the facility so that his car wouldn’t be there, so if they dropped in they wouldn’t know he was there,” Banning told the paper. “So for about a three-week period, he had the flu — we had every excuse in the world. We were just trying to rip weight off him again. And it ballooned way out of control.”

In 2011, the trainer says, Sandoval gained 21 pounds in just 21 days putting his ability to get around the field in danger.

“I was coming in seven days a week, he was training three times a day on six days, and on Sundays he was training twice,” Banning added. “It was that bad. I mean, it got out of control.”

The trainer’s comments about the player’s weight problems are substantiated by reports revealing that when Sandoval was with the San Francisco Giants the team went to the extreme of telling hotel staff not to serve him if he tried to use room service.

According to Comcast Sports Net’s Sean McAdam, Sandoval had such a problem the team went out of its way to help him prevent it.

“This is how concerned the Giants were when he played for them,” McAdam said on a recent broadcast of Boston’s Toucher and Rich, “they would make special arrangements at the hotel the Giants were staying in to not allow him to order room service. They would tell the front desk management, ‘If he calls down for room service at night after games, do not send anything to this room.’ They went to great measures to try to cut down on those eating binges, and it would only work for a time because he would find someplace to get food.”

Follow Warner Todd Huston on Twitter @warnerthuston or email the author at igcolonel@hotmail.com