RCT Finds Time-Restricted Eating Cuts HbA1c 0.5 Points in Obese Type 1 Diabetes Adults

The University of Illinois Chicago trial randomized participants to time-restricted eating without calorie counting, 25% daily calorie reduction, or usual diet. Primary endpoint was change in HbA1c measured by standard assay at baseline and six months. Secondary safety monitoring tracked continuous glucose readings and ketone levels for diabetic ketoacidosis events.

Time-restricted eating produced a 0.5-point HbA1c drop, outperforming the calorie-reduction arm by 0.3 points. Absolute rates of level 2 hypoglycemia and ketoacidosis remained under 2% in both intervention groups, matching control. The design isolated eating-window effects from overall energy deficit in a population where exogenous insulin already fixes total daily dose.

Prior intermittent-fasting research focused on type 2 diabetes or healthy adults; this is the first RCT in type 1 diabetes and the first to target the 0.5% of U.S. adults who have both type 1 diabetes and obesity. The 0.5-point reduction matches the effect size of adding a single oral agent in type 2 trials but avoids extra medication burden.

Next steps require a multisite trial of at least 200 participants powered for 12-month durability and stratified by insulin pump versus multiple daily injections to test generalizability before guideline consideration.