Noon-to-8 eating window lowers blood sugar in type 1 diabetes

At noon, the eating clock opened. It closed again at 8 p.m. For six months, that was the schedule assigned to one group in a University of Illinois Chicago study testing time-restricted eating in adults with type 1 diabetes. The 32 participants were randomly placed in one of three groups, making the result a controlled human trial rather than a dietary anecdote.

The participants had type 1 diabetes, a condition in which the body produces little or no insulin, and were classified as obese according to Centers for Disease Control and Prevention body-mass-index criteria. One group ate only during the eight-hour window without counting calories. A second cut calorie intake by 25%. The control group changed nothing.

After six months, the time-restricted group had lower blood sugar than the calorie-counting group. The HbA1c blood test showed an average decrease of about 0.5 percentage points. That comparison matters because it suggests that limiting when people eat may help control blood sugar without requiring them to track every calorie.

The safety signal was also part of the result. The UIC team found that time-restricted eating did not increase the risk of extreme high or low blood sugar or diabetic ketoacidosis, a life-threatening lack of insulin. Krista Varady, the kinesiology and nutrition professor who led the study, called it a first step toward a potentially safe method—not a basis for changing treatment alone.

So what does it change, concretely? For some adults with type 1 diabetes who also have obesity, an eating window could become another option to discuss with an endocrinologist or health care provider, alongside existing care. The evidence remains narrow: the trial involved 32 people from around Chicago, and Varady says larger, multisite studies are needed to see whether the findings hold more broadly.