Adults with Type 1 diabetes and obesity who limited their daily eating to an eight-hour window showed measurable improvements in blood sugar control over six months, according to a randomized controlled trial from the University of Illinois Chicago. The study, published in the journal Diabetes Care in September 2026, enrolled 32 participants and is described as the first to examine time-restricted eating in this population.
What the Study Tested
Researchers randomly placed 32 adults with Type 1 diabetes and obesity into one of three arms for six months. One arm followed an eight-hour eating window between noon and 8 p.m. without counting calories. A second arm reduced calorie intake by 25%. A control group made no changes to its usual behavior. All participants were recruited from the Chicago area.
What Changed 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 prior several months, fell by about 0.5% on average in the time-restricted group. The researchers also found no increase in the risk of dangerously low or high blood sugar among participants following the restricted schedule, and the approach did not raise the risk of diabetic ketoacidosis, a life-threatening condition that occurs when the body does not have enough insulin.
Why This Group Matters
Type 1 diabetes is a chronic autoimmune condition in which the body produces little or no insulin, the hormone needed to move glucose from the bloodstream into cells. The condition affects less than 1% of people in the U.S., according to the study. Unlike Type 2 diabetes, Type 1 cannot be reversed through lifestyle changes alone. The combination of Type 1 diabetes and obesity applies to about 0.5% of the total U.S. population, based on the study’s enrollment criteria.
Obesity rates in American adults climbed from 30.5% in 1999-2000 to 41.9% in 2017-2020, according to CDC data referenced in the study.
How Time-Restricted Eating Fits In
Time-restricted eating is a form of intermittent fasting that limits food consumption to a specific daily window without requiring calorie counting. Earlier research has examined its effects on metabolic parameters, and prior human studies have focused primarily on Type 2 diabetes or general obesity rather than Type 1 diabetes. This trial was designed to address that gap.
Caveats From the Study
The researchers emphasized several limits. The sample size of 32 participants is small. The trial was conducted at a single site. Participants were followed for six months, a relatively short window for a chronic condition. These factors restrict how broadly the findings can be generalized.
The researchers also stressed that anyone considering changes to eating habits, especially people with diabetes, should work closely with an endocrinologist or healthcare provider first. Independent guidance on intermittent fasting notes that long periods without eating may be too extreme for some older adults, people with diabetes, and those who must take certain medications at designated hours.
What Comes Next
Researchers stated they next hope to run larger, multi-site trials to test whether the findings hold up in a broader population. Such trials would need to enroll more participants and follow them for longer periods to assess whether the blood sugar improvements persist and whether any safety concerns emerge over time. No clinical recommendations can be made yet.
The study was funded and conducted by University of Illinois Chicago investigators. The research was led by a longtime intermittent fasting researcher at UIC, working with other UIC co-authors, and published in September 2026.
FAQ
What did the eight-hour eating window study find for people with Type 1 diabetes?
After six months, participants who limited eating to an eight-hour window between noon and 8 p.m. saw HbA1c fall by roughly 0.5% on average, with no increase in dangerous blood sugar swings or diabetic ketoacidosis.
How many people were in the study, and who ran it?
The trial enrolled 32 adults with Type 1 diabetes and obesity from the Chicago area. It was a randomized controlled trial led by University of Illinois Chicago researchers and published in the journal Diabetes Care in September 2026.
Is time-restricted eating safe for someone with Type 1 diabetes?
The researchers said the findings are only an initial step and that anyone with diabetes should consult a medical professional before changing eating habits. The small sample size and single-site, six-month design limit how broadly the results apply.
