Dietary Approaches for the Management of Overweight and Obesity in Type 1 Diabetes

Although type 1 diabetes (T1D) has traditionally been considered a disease associated with a lean phenotype, it is estimated that up to 2 out of 3 people living with T1D are overweight or obese, factors linked to an increased risk of complications in these patients. The available evidence regarding nutritional strategies for weight loss in T1D is very limited, and clinical trials are needed to determine how to effectively and safely promote weight loss in this population. In recent years, low-carbohydrate diets and several intermittent fasting protocols have demonstrated efficacy in promoting weight loss both in patients with type 2 diabetes and in patients with obesity without diabetes. This study will evaluate the efficacy of moderate carbohydrate restriction, time-restricted eating, and standard calorie restriction for weight loss in adults with T1D and overweight/obesity.

Inclusion Criteria: * T1D treated with intensive insulin therapy (multiple daily insulin injections or continuous subcutaneous insulin infusion systems) * HbA1c 6.5-9% * BMI ≥ 25 and ≤ 45 kg/m2 * Active prescription and use of CGM * Active prescription for glucagon Exclusion Criteria: * Pregnancy, pregnancy planning, or breastfeeding * Forms of diabetes other than T1D, or T1D duration \< 1 year * Previous cardiovascular events (acute myocardial infarction or stroke), heart failure, unstable coronary artery disease, chronic kidney disease with estimated glomerular filtration rate ≤ 30 mL/min/m², cirrhosis, or presence of active cancer * Unstable diabetes, episodes of glycemic decompensation (diabetic ketoacidosis) or severe hypoglycemia (level 3) within the past year. * Planned change in treatment during the study (switching from multiple daily insulin injections to continuous insulin infusion, or vice versa) * Use of sodium-glucose cotransporter 2 inhibitors, glucagon-like peptide-1 (GLP-1) receptor agonists, GLP-1/GIP agonists, or other medications that may influence weight loss * Having experienced a change in body weight greater than 5% within the 3 months before screening * Following any form of diet prior to inclusion, carbohydrate restriction, or intermittent fasting * History of eating disorders or alcohol abuse * Inability to follow the dietary recommendations * Presence of other conditions that, in the investigator's judgment, may compromise participation in the study.