At age 15, Sara Pastor discovered that she could use her diabetes to control her weight. All she had to do was stop taking her insulin.

“The first day it ever happened, it was Halloween. I ate some candy and forgot to take insulin,” recalled Pastor, now 22 and a student at the University of California, Berkeley. “I got on the scale the next morning and had lost weight.”

She put two and two together. Since childhood, she had managed her diabetes by meticulously dosing herself with insulin and almost always avoiding sweets—and now, it seemed that if she broke those rules, the pounds would come off.

“A couple of months later I went to 7-Eleven to get a candy bar and doughnut and said I won’t take my insulin just this one time. I will get this out of my system,” she says. But one time led to a few more sugar binges, and then more frequent ones. Within a few months, Pastor was struggling with “diabulimia,” the lay term for the dual diagnosis of Type 1 diabetes and an eating disorder.

Some studies report that people with Type 1 diabetes, an incurable condition in which the body produces little or no insulin, are twice as likely as non-diabetics to develop an eating disorder, often by underdosing their insulin. This insulin restriction, in turn, leads to further health problems—one study shows they are three times more likely to die of diabetes-related complications than those who follow their medication regimen.

Treating diabetes patients with eating disorders comes with unique, complex challenges, says Marcia Meier, a diabetes nurse educator at the Melrose Center in Minneapolis, one of only a few facilities in the country that specializes in diabulimia.

“With diabetes there is a focus on numbers: What is your blood sugar? … How many carbohydrates have you consumed?” she explains. But “with eating disorders, people need to learn to let go of the obsession with numbers. So there is a conflict in treatment approaches.”

Over time, diabulimia can have potentially devastating medical consequences, says Shanti Serdy, an endocrinologist at the Joslin Diabetes Center in Boston. “Unfortunately I have seen patients develop complications that normally would happen much later, if at all, such as loss of vision and kidney failure,” she says.

The condition can also quickly turn fatal: One effect of insulin deprivation is that the body can no longer use glucose for energy, and so burns fat as an alternative source. This results in the buildup of a toxic substance called ketones, which can rapidly lead to severe dehydration, coma, and sometimes death.

Over time, Serdy, who works in tandem with a psychologist to treat diabulimia patients, has learned the warning signs. “The first clue to me that patients are purposely restricting insulin is an extremely high A1c,” a test measuring average blood-sugar levels over the past few months, “despite that they have a clear understanding of diabetes self-management,” she said. A healthy A1c level is around 6.5; Serdy has seen diabulimia patients with levels as high as 17. Mood swings and exhaustion are also common, as is avoidance—often, patients will cancel appointments or “forget” to bring diabetes records to their doctors’ visits to avoid being caught.

Pastor managed to hide what she was doing from her parents, and even her doctor, for months. It was easy to do, as she had always insisted on giving herself injections and monitoring her sugar on her own. When her sugar was higher than normal, her health providers assumed she was simply rebelling against the strict diet that her disease demanded by sneaking a few treats.

After a couple of months, she was crashing, too tired some days to stand up or talk. She recalls lying on the couch, hearing her parents try to wake her and whispering they were afraid she was slipping into a coma. Finally, she told them what she had been doing, kicking off five long years of therapy and repeated hospitalization.

Often, Type 1 diabetics’ risk of developing an eating disorder has to do with the messages they receive about their disease early in life, says Dawn Taylor, a psychologist at the Melrose Center. After a child is diagnosed, families typically change how they eat and establish new rules around food—an important part of managing the disease, but also often a tricky line to walk.

“A message gets into [the young diabetic’s] belief system that desserts are bad,” Taylor said, and “a lot of them say their doctors tell them they will gain weight on insulin, which they interpret as insulin equals fat.” This can lead to an all-or-nothing mentality—and then, when patients do allow themselves certain foods, they can feel out of control. That’s often when the deliberate insulin restriction begins, though many fail to recognize their behavior as a serious problem.

“You hear denial. They say, ‘I don’t have to be talked into eating, and I’m not making myself vomit.’ So they think they don’t have an eating disorder,” says Meier.

The patients that Serty has seen turn around have worked with specialized health-care teams and had their families involved in recovery. The latter is especially important, she says, since some of the beliefs leading to eating-disorder behaviors in diabetics begin with the actions and words of well-meaning parents. Relapse rates are high—recent research found a 53-percent chance of recurrence within six years of remission—but Meier says that with an ongoing support system, patients are more likely to eventually go back to testing their sugar regularly, eating normally, and taking their insulin the way it’s prescribed.

After struggling for years, Pastor entered a residential treatment program for diabulimia at the Center for Hope of the Sierras in Reno, Nevada, at age 21. Someone sat with her through every meal, watched her take her insulin, and woke her twice a night to monitor her sugar. But she also learned to look out for herself.

“They taught me skills like intuitive eating, where you listen to your body cues and eat based on them. If your body says ‘I want a cookie now,’ you eat it. Then you check in with yourself and pay attention to how full and satisfied you are,” she said. “I am no longer scared of food or obsessed with it—when you feel like you can have a burger whenever you want, you don’t want it as much.” And after finishing treatment in March of this year, she’s gone back to diligently taking her insulin.