Can People With Type 1 Diabetes Safely Try Intermittent Fasting?
By Dr. John Bartemus, DC, CFMP, Functional Medicine Charlotte, PC. Published September 18, 2026.
Short answer: A 2026 randomized controlled trial in Diabetes Care offers the first real evidence that time-restricted eating, a form of intermittent fasting, may be done safely by some adults with Type 1 diabetes. Over six months, an 8-hour eating window (noon to 8 p.m.) improved blood sugar control, lowering HbA1c by about 0.5 percent, without increasing the risk of dangerous blood sugar swings or diabetic ketoacidosis. This is genuinely encouraging, but it is a small, early study of 32 people conducted under medical oversight. It is not a reason for anyone with Type 1 diabetes to change how they eat without close guidance from their endocrinologist.
Intermittent fasting has been studied extensively in weight loss and Type 2 diabetes, but Type 1 diabetes has been treated as off-limits, and for understandable reasons. In Type 1 diabetes the body makes little or no insulin, so every change in meal timing has to be matched by careful insulin adjustment, and the risks of low blood sugar and diabetic ketoacidosis are real. A new study is the first to test the approach directly, and the results are worth understanding, along with the strong cautions that come with them.
What the researchers did
A team at the University of Illinois Chicago, led by intermittent-fasting researcher Krista Varady, enrolled 32 adults from the Chicago area who had Type 1 diabetes and were also classified as obese. Participants were randomly assigned for six months to one of three groups. The first followed time-restricted eating, consuming food only between noon and 8 p.m. and, importantly, not counting calories. The second reduced calorie intake by 25 percent. The third made no changes and served as the control. The study was published in Diabetes Care.
What they found
After six months, the time-restricted eating group showed better blood sugar results than the calorie-reduction group. HbA1c, a blood test that reflects average blood sugar over the previous two to three months, fell by about 0.5 percent on average in the time-restricted group. A change of roughly half a percentage point in HbA1c is clinically meaningful, and the participants achieved it without tracking calories, simply by narrowing when they ate.
The safety findings are the most important part. The researchers reported no increase in the risk of dangerously high or low blood sugar among people following the restricted schedule, and no increase in the risk of diabetic ketoacidosis, a life-threatening complication that occurs when the body lacks enough insulin. As the lead researcher put it, this is a first step toward showing that time-restricted eating “could be a safe, potentially effective method” for people with Type 1 diabetes to manage blood sugar.
A functional medicine perspective
What stands out here is the leverage of meal timing. The time-restricted group improved blood sugar without calorie counting and did so more effectively than the group that actively cut calories. That fits a broader principle worth taking seriously: when you eat can influence metabolic health, not only how much you eat. Concentrating food intake into a defined daytime window aligns eating with the body’s circadian rhythm and gives the system extended daily periods without incoming glucose, which may improve how the body handles blood sugar. The same underlying issue of glucose regulation sits at the center of far more common conditions, as I discuss in my article on insulin resistance.
That said, Type 1 diabetes is fundamentally different from the insulin resistance seen in Type 2. It is an autoimmune condition in which insulin-producing cells are destroyed, so time-restricted eating is not a treatment for the disease and does not reduce the need for insulin. It is, at most, a possible tool to support blood sugar management alongside standard medical care.
Important cautions
The researchers themselves were careful, and so should we be. This was a single, small study of 32 people who also had obesity, all conducted with medical oversight. It shows that the approach was safe and helpful in this specific group over six months. It does not establish that fasting is safe for everyone with Type 1 diabetes, and it is not a do-it-yourself protocol. Meal timing directly affects insulin dosing, and getting that wrong can cause hypoglycemia or ketoacidosis. Anyone with Type 1 diabetes who is interested in time-restricted eating should only pursue it in partnership with their endocrinologist, who can adjust insulin and monitoring accordingly. The study’s author said it plainly: people making changes to their eating, especially those with diabetes, must work closely with their healthcare provider.
Watch: can Type 1 diabetics safely use intermittent fasting?
A short explainer on this question and what the new research does and does not show.
The bottom line
For years, intermittent fasting and Type 1 diabetes were considered a risky combination. This 2026 trial is the first to test the pairing head-on, and it found that a simple 8-hour eating window improved blood sugar without raising the risk of serious complications, at least in a small group under supervision. That is a meaningful and hopeful result. It is also an early one. The right response is not to start fasting on your own, but to bring this evidence to your endocrinologist and decide together whether it fits your situation.
Frequently asked questions
Can people with Type 1 diabetes safely do intermittent fasting?
A 2026 randomized trial in Diabetes Care found that an 8-hour eating window improved blood sugar in adults with Type 1 diabetes and obesity without raising the risk of dangerous blood sugar swings or diabetic ketoacidosis. It was a small, supervised study and is not a reason to change eating habits without your endocrinologist’s guidance.
What did the 2026 study find?
Thirty-two adults with Type 1 diabetes and obesity were randomized for six months to time-restricted eating (noon to 8 p.m.), a 25 percent calorie reduction, or no change. The time-restricted group had better blood sugar results than the calorie-reduction group, with HbA1c falling about 0.5 percent, and no increase in serious complications.
How much did blood sugar improve?
HbA1c fell by about 0.5 percent on average over six months in the time-restricted eating group, a clinically meaningful change, achieved without counting calories.
Should I try time-restricted eating if I have Type 1 diabetes?
Not on your own. Meal timing affects insulin dosing and the risk of hypoglycemia and ketoacidosis. Discuss it with your endocrinologist so insulin and monitoring can be adjusted safely.
About the author: Dr. John Bartemus, DC, CFMP, is a functional medicine practitioner, educator, speaker, and Amazon international number one best-selling author, focusing on autoimmunity, cardiometabolic health and root-cause medicine through Functional Medicine Charlotte, PC.
This article is for educational purposes only and is not medical advice. Type 1 diabetes is a serious condition that requires insulin and ongoing medical management. Do not change your eating pattern, insulin dosing, or any part of your treatment without your endocrinologist or healthcare provider.
Sources: Runchey MC, et al. “Efficacy and Safety of Time-Restricted Eating in Adults With Type 1 Diabetes: A Randomized Controlled Trial.” Diabetes Care, 2026. DOI 10.2337/dc26-1093. University of Illinois Chicago, reported via ScienceDaily, September 10, 2026.
