Intermittent fasting (IF), going without food for a period of time rather than reducing daily caloric intake, may be a good choice for people with type 2 diabetes.1 The eating plan, which has gained popularity over the past few years, has proven easier for some people to follow than calorie-restricted diets.
“It’s an ancestral way of eating,” says Linda Sartor, RD, MA, CDE, LDN, Diabetes Nutritionist, Penn Rodebaugh Diabetes Center at Penn Medicine. “Throughout millennia, man didn’t always have a constant supply of food, there were times of plenty and then nothing.”
“There is no one definition of intermittent fasting,” says Sartor, who has helped people with type 2 diabetes adapt to IF. “How to accomplish IF varies—some people eat 8 hours then fast while others eat normally five days a week and fast for two consecutive or non-consecutive days. Many people love the idea of eating only two meals a day, or—if fasting is too daunting—restricting yourself to 600 calories on fasting days, or simply not eating from 7 at night until 7 in the morning.”
Another approach is to try knocking off 600 calories from your daily intake. "For a man, who would normally eat 2000 calories, that would bring him down to 1400-1500; for a woman who would normally eat 1500 to 1800, it would knock down her intake to 1000 to 1200.” (For reference: One cup of high-end ice cream has about 600 calories; so do 2 slices of 14" pizza with pepperoni.)
“We used to recommend grazing for people with type 2 diabetes—three meals and three snacks a day—but that didn’t prove itself,” Sartor explains. “People tended to eat six meals. Now we say nothing after 7 pm unless you have a low blood sugar, which is a kind of IF. I’ve had a number of folks with type 2 in our practice who had safe and effective weight loss on IF. They lowered their A1C’s and some reduced or got off their medications.”
The biggest downside to intermittent fasting for people with type 2 is the danger of hypoglycemia or low blood sugar.2 For this reason, it is recommended that type 2s who wish to follow these diets consult with a nutritionist or their healthcare practitioner, both to carefully monitor their sugars and to adjust medications if hypoglycemia becomes an issue.
A recent study3 examined the dangers of low blood sugars while fasting, and found that while hypoglycemia was a risk when people with type 2 diabetes tried IF, “with education and medication reduction” fewer low blood sugar episodes occurred.
In the research, 37 participants were divided into two groups, one of which fasted on two nonconsecutive days and the other on two consecutive days over 12 weeks. Improvements were seen in weight, A1C, fasting glucose and quality of life for all participants, with an average rate of 1.4 hypoglycemic events for those on medications that produced hypoglycemia.
Occasionally skipping a meal won’t cause a problem for most people with type 2 diabetes, says Mario Skugor, MD, a clinical assistant professor of medicine at the Endocrine and Metabolic Institute, Cleveland Clinic. “There is no good reason they can’t in order to lose weight, but if you’re on a sulfonylurea skipping meals could cause lower blood sugars.”
“On the other hand, if you are on metformin, GLP-1s, DDP-4s or newer insulin analogs you can probably plan to skip a meal without giving yourself low blood sugar,” the endocrinologist says. “With the newer insulin, you don’t need to eat on a schedule, which is one of the advantages of modern medication.”
"But," he cautions, "One diet is not any better than another."
Another small but recent Canadian study also found advantages of intermittent fasting for people with type 2 diabetes4.
Three men, aged between 40 and 67, tried intermittent fasting to see if it would improve their health and lessen their reliance on insulin and medication. The men had diabetes for varying amounts of time—between 10 and 25 years and were taking various drugs to control their disease as well as daily units of insulin. In addition to type 2 diabetes, they all had high blood pressure and high cholesterol.
One of the men fasted for three days out of the week; the other two fasted on alternate days for 24 hours. On fast days they were permitted very low callow-calorie, such as tea/coffee, water or broth, and one very low-calorie meal for dinner.
They all participated in a 6-hour long nutritional training seminar to become educated on the development of diabetes and it's impact on the body as well as learning how diabetes can be managed through diet.
In less than a year of following a fasting routine, their average A1C levels, weight and waist circumference dropped to more healthy numbers. In addition, all three men were able to stop insulin injections within a month of starting their fasting schedule—in one case this took only five days. Two of the men were also able to stop taking their diabetic medication and the third man discontinued three of the four drugs he was taking.
Pregnant women are not advised to follow this regimen. And while fasting for type 2s may be beneficial, Sartor notes such a plan is much more tricky for people with type 1.
“Fasting leads to breaking down fat for fuel, which leads to more ketones in the bloodstream and can lead to diabetic ketoacidosis. Type 1s need very close monitoring to avoid this,” she says.
“Overall, IF has been shown to be good for the brain,” says Sartor. “It helps with mental clarity, boosts antioxidants, protects the body from free radicals, increases energy production in the mitochondria and helps with autoimmune diseases.”
“There is also lots of research that shows that IF in type 2 diabetes helps reduce insulin resistance, one of the major problems in people with type 2. IF helps people use insulin more efficiently,” she says. “While the literature is clear that any approach to losing weight lowers inflammation, IF seems also to decrease visceral fat which leads to fewer metabolic issues and a lower rate of heart disease.”
According to Amy Hess Fischl, MS, RD, LDN, BC-ADM, CDE a program coordinator for the Teen and Adolescent Diabetes Transition Program at the University of Chicago’s Kovler Diabetes Center, patients should not “jump in without consulting with a registered dietitian nutritionist.”
“For the newly diagnosed who are not on any diabetes medications or some people with prediabetes without other pre-existing conditions, intermittent fasting may help to jump start weight loss efforts,” says Hess-Fischl. “But each person should be assessed by an RDN to see if it's the right option for them.”
“When it comes to nutrition, one size does not fit all.”