Personal trainer Robyn Baker does a yoga tree pose at the Healthfit 4 Life studio at Personal Care Physicians in Newport Beach, California.

SANTA ANA, Calif. — Obese diners are free to gorge at McDonald’s. Gambling addicts can spend every last dollar in a casino. Cancer patients are allowed to buy cigarettes.

So should gyms be different, as far as members who exercise too much and often have eating disorders?

That was the scenario raised in a letter to the British Medical Journal by an adolescent health researcher troubled by the workout routine of an extremely thin, twentysomething woman he saw during every visit to the gym.

"While I’m trying to wake up on the treadmill, Amy is coming out of the early morning aerobics class, having finished an hourlong workout," wrote Rony Duncan of Australia. "While the others head to the showers, Amy heads to the bicycles. Often she is still there by the time I leave. … Having shared several concerned glances with fellow gym members, I suspect I’m not the only one who is worried."

While Duncan notes that businesses such as fast food restaurants and casinos have no obligation to the well-being of their customers, he wonders whether gyms, which exist to promote healthy living, should be held to a higher standard.

Some fitness centers say they are aware of the problem. An article posted on the International Health, Racquet & Sportsclub Association’s website includes tips on what to do if a member is suspected of having an eating disorder. In educational material posted there, one expert estimated 90 percent to 95 percent of people with eating disorders use a fitness center.

San Diego State University has a public service campaign targeting excessive exercise, sometimes called exercise bulimia or anorexia athletica, which asks: "Are you getting too much of a good thing?"

Irvine, Calif., resident Robyn Baker, a personal trainer and Pilates instructor, understands the compulsion.

She was anorexic at 18, but after reaching a healthier weight, she moved to over-exercising. She didn’t miss a three-hour workout in five years.

Looking back, Baker said some gym members must have been disturbed by her. But she also received compliments.

"People would come up to me and say, ‘You look great; you’re in here all the time. That’s awesome.’ They would praise me and tell me I should be a model and I’m so skinny and I’m so lucky. In my head, my eating disorder loved to hear that."

Baker has worked in a number of large gyms and said none had policies for handling a member who appeared to work out too much.

"It’s a very touchy subject," Baker said. "It’s not like a bar; they can’t cut you off. When you go to a bar and you see someone drunk, a bartender isn’t going to give you any more beer. If you walk into a gym at 2 percent body fat and bones are sticking out, they don’t say you can’t come in."

Baker said she would love to see gyms offer education on signs of eating disorders, as well as how to approach a member or personal training client.

"It is a growing problem, and people don’t know how to address it, so they don’t. They don’t want to talk about it because it’s uncomfortable. It’s taboo."

Irvina Kanarek, founder of Rewrite Beautiful, a Newport Beach, Calif., nonprofit group that uses art against eating disorders, said those recovering from eating disorders can be triggered by seeing gaunt women exercise excessively in the gym.

She wishes health clubs had counselors or psychologists available. But she also said that such intervention doesn’t always work.

"I’ve also had an experience when I was at the gym. I had a woman trainer who was taking my body mass index," Kanarek said. "She mentioned to me, ‘Your BMI is really low.’ I was at the point where I wasn’t really admitting I had an eating disorder."

The trainer proceeded to talk about the risk of eating disorders and too much exercise.

"I was completely offended and upset with her, and I never went back to that gym."

But Kanarek, who overcame anorexia, bulimia and compulsive overeating, said if she saw a gym-goer who appeared to be struggling, she would try to reach out.

"Personally, if I was to see someone looking that way, I would definitely become a friend of theirs," she said. "I would chat with them. I would get to know them. I would say I’ve struggled with this."