The new case report says the three patients also lost weight, and their HbA1Cs, a measure of blood sugar levels, improved.
“People are focused on giving drugs to Type 2 diabetes, but it’s a dietary disease,” said study author Dr. Jason Fung, medical director of the Intensive Dietary Management Program in Toronto.
Experts say this clashes with the widely held belief that diabetes is strictly a chronic, irreversible disease — though Fung said that’s been changing in recent years.
“In general, the concept of reversing or curing diabetes … is not well-accepted in the medical field,” said Dr. Abhinav Diwan, associate professor of medicine, cell biology and physiology at the Washington University School of Medicine in St. Louis. “It is not even a therapeutic goal when people start to treat diabetics.”
In the study, patients followed 24-hour fasts several times a week. They ate only dinner on fasting days but could drink water, coffee and broth throughout. They were all men, ages 40, 52 and 67, who had been diagnosed with diabetes 20, 25 and 10 years prior, respectively.
This is different from Type 1 diabetes, an autoimmune condition in which the pancreas doesn’t produce much, if any, insulin. Fasting for those with Type 1 diabetes “may be unsafe due to the increased risk for hypoglycemia,” said Diwan, who was not involved in the new study.
When it comes to this field of research, he said, “these are early days but very exciting.” The new report is not a definitive study, he added; it has a small sample size, no control group and limited followup. Existing research in humans is also difficult to compare because it is largely observational, and how to implement fasting hasn’t been standardized, Diwan said.
“It is very clear that people who can lose weight have better blood sugar control … [and] sometimes can get off insulin if not too advanced in their disease,” said Dr. Robert Gabbay, chief medical officer at the Joslin Diabetes Center, a nonprofit research and care center in Boston affiliated with Harvard Medical School.
“The most established example of that are people that have bariatric surgery,” he added. “They lose significant amounts of weight, and some of them get off all medications.”
Gabbay, who was not involved in the new report, calls this a “remission” of diabetes rather than “cure” because, “as far as we know, it’s still worthwhile having a yearly eye exam, having a screening for kidney disease and nerve damage, even in those people that normalize their blood sugars, because they may be at continued risk.”
“Although, honestly, there aren’t enough of those people to know.”
Experts like Fung are calling for more research on this topic, which has not gotten much attention from the broader scientific community.
“Intermittent fasting has been in a hinterland for many, many years. There’s been really no data on it,” Fung said, adding that his proposals for larger studies on fasting and diabetes have been denied by two Toronto hospitals.
He said he’s seen thousands of patients in his program, and the new report, which took two years to publish and includes only three patients, is part of an ongoing effort to show early evidence and advocate for larger studies.
But without randomized trials, Diwan said, it’s tough to say how effective intermittent fasting is, what’s the best way to do it and how sustainable it might be in the long run.
At the very least, “intermittent fasting has been practiced across various cultures,” Diwan said, citing his own Hindu culture as an example. “So that tells you right off the bat that it’s a doable thing.”
“Clearly, there is need for caution, because diabetic people are prone to hypoglycemic episodes, and hypoglycemia can be fatal,” Diwan said. “People do not want to put them themselves at risk by fasting without consulting a doctor.”
Gabbay said the new paper accomplishes its goal of warranting further study, but on its own, it’s a success story about just three people — and one would be “hard-pressed to draw any conclusions from this kind of work.”
“We always worry when reports of dramatic results are presented, as they may be misinterpreted by people,” he said. “In the world of diet and weight loss, things really catch on quickly.”