Intermittent fasting in type 1 diabetes: new RCT results

What happened: intermittent fasting and type 1 diabetes tested in a trial

A University of Illinois at Chicago (UIC) research team reported results from a randomized controlled trial of intermittent fasting—specifically time-restricted eating—in adults with type 1 diabetes.

The study, published in Diabetes Care, tested whether limiting eating to a daily window could help participants control blood sugar while staying safe from severe highs, severe lows, or diabetic ketoacidosis.

• Journal: Diabetes Care (2026), randomized controlled trial
• Lead investigator quoted: Krista Varady, kinesiology and nutrition professor at UIC
• Intervention: time-restricted eating (eating only between noon and 8 p.m.) with no calorie counting

What the evidence shows about intermittent fasting and type 1 diabetes

In this randomized controlled trial, 32 adults with type 1 diabetes who were also classified as obese were assigned for six months to one of three approaches: time-restricted eating (noon–8 p.m.), a 25% calorie reduction, or no behavior change.

After six months, the time-restricted eating group showed reduced blood sugar levels compared with the calorie-counting group, with an average HbA1c decrease of about 0.5 percentage points, and the researchers reported no increased risk of extreme high or low blood sugar levels or diabetic ketoacidosis.

• Participants: adults with type 1 diabetes and obesity (CDC BMI classification), recruited around Chicago
• Duration: six months
• Comparison groups: time-restricted eating vs 25% calorie reduction vs control
• Outcome noted: HbA1c average decrease ~0.5 percentage points in time-restricted group vs calorie-counting group
• Safety noted: no increased risk of extreme high/low blood sugar or diabetic ketoacidosis reported in the time-restricted group

Who this applies to—and what it does not prove yet

This intermittent fasting and type 1 diabetes study applies most directly to adults with type 1 diabetes who also meet criteria for obesity, because that is the group the researchers recruited and studied.

It does not establish that time-restricted eating works the same way for all people with type 1 diabetes, because the trial was small (32 participants) and conducted in one region, and the authors describe it as an initial step toward larger, multisite research.

• Population studied: adults with type 1 diabetes and obesity
• Setting: participants recruited around Chicago
• Scale: small trial (32 people)
• Next step stated by investigators: larger, multisite studies to test whether results hold more broadly

Practical context for metabolic health: what time-restricted eating looked like

In this trial, time-restricted eating meant eating only between noon and 8 p.m., without calorie counting, for six months.

Because type 1 diabetes management involves insulin and glucose monitoring, the investigators emphasized that anyone changing eating habits—especially people with diabetes—should work closely with their endocrinologist or health care provider to find an approach that fits them.

• Time window used: noon to 8 p.m.
• No calorie counting in the time-restricted group
• Clinical coordination emphasized by the study’s authors for anyone changing eating habits with diabetes

Caveats and why safety reporting matters in intermittent fasting and type 1 diabetes

Safety is a central concern in intermittent fasting and type 1 diabetes because skipping or delaying meals can raise questions about severe hypoglycemia, severe hyperglycemia, and diabetic ketoacidosis; in this trial, the researchers reported no increased risk of those extreme events in the time-restricted eating group.

Even so, the investigators framed these results as early evidence and described the work as a first step, with larger studies needed before the findings can be treated as universal guidance.

• Reported in this trial: no increased risk of extreme high/low blood sugar or diabetic ketoacidosis with time-restricted eating
• Study framing: “first step” toward showing time-restricted eating could be safe and potentially effective