Intermittent Fasting in Adults With Type 1 Diabetes

The majority of adults with type 1 diabetes (T1DM) have either overweight or obesity. As such, dietary management has been recommended as an adjunct to insulin treatment to improve glycemic control and facilitate weight loss in patients with T1DM. Daily calorie restriction (CR) is the main diet prescribed to patients with T1DM for weight loss. However, many patients find it difficult to adhere to CR because calorie intake must be vigilantly monitored every day. In light of these problems with CR, another approach that limits timing of food intake, instead of number of calories consumed, has been developed. This diet is called "time restricted eating" (TRE) and involves confining the period of food intake to 6-8 h per day. TRE allows individuals to self-select foods and eat ad libitum during a large part of the day, which greatly increases compliance to these protocols. The simplicity of TRE, its accommodation of dietary preferences, and associated weight loss may translate to improved glycemic measures in patients with T1DM. The present study will be the first randomized controlled trial to compare the effect of TRE versus CR for weight management and improved glycemic control in adults with obesity and T1DM.

Study Overview

• Status: Completed
• Conditions: Obesity; Type 1 Diabetes
• Intervention / Treatment: Other: Daily calorie restriction; Other: Time restricted eating

• Study Type: Interventional
• Enrollment (Actual): 32
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Illinois
    • Chicago, Illinois, United States, 60612
      • University of Illinois Chicago

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Previously diagnosed with T1DM and currently using insulin
• HbA1c: 6.5-9.5% (regardless of medication use)
• Age between 18 to 75 years old
• BMI between 25 and 50 kg/m2
• Independently living (i.e., subjects who do not live in a nursing home or institution)
• On either multiple daily doses of insulin injections (MDII) or using an insulin pump (with or without closed loop feature)
• Active prescription for daily use of a continous glucose monitor (CGM) or willing to be provided with a CGM during the study (at no cost)
• Active prescription for glucagon

Exclusion Criteria:

• History of severe hypoglycemia defined as requiring help from others, needed to use emergency glucagon administration in the past 6 months.
• Medical history of heart failure, unstable coronary artery disease, chronic obstructive pulmonary disease, requiring oxygen, cirrhosis, active cancer, history of stroke, cognitive impairment, end stage renal disease (eGFR ≤30 ml/min/m2)
• Previously diagnosed with T2DM
• Have a history of eating disorders (anorexia, bulimia, or binge eating disorder)
• Are not weight stable for 3 months prior to the beginning of study (weight gain or loss > 4%)
• Are not able to keep a food diary for 7 consecutive days during screening
• Are taking certain drugs that have significant weight loss outcomes (weight loss medications, specifically GLP1 agonist, GLP-1/GIP agonists)
• Are eating less than a 10-hour window at baseline
• Are perimenopausal (menses does not appear every 27-32d)
• Are pregnant, or trying to become pregnant
• Are night shift workers

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Daily calorie restriction (CR); 25% energy restriction every day Diet counseling provided	Other: Daily calorie restriction; 25% energy restriction every day Diet counseling provided
No Intervention: Control; Ad libitum food intake, eating over more than 10 hours per day
Experimental: Time restricted eating (TRE); 8-h eating window Ad libitum food intake from 12-8 pm every day Fasting from 8-12 pm every day (16-h fast)	Other: Time restricted eating; 8-h eating window Ad libitum food intake from 12-8 pm every day Fasting from 8-12 pm every day (16-h fast)

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in percent body weight	Measured by an electronic scale	Measured at baseline and month 6

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in total time in euglycemic range	Measured by continuous glucose monitor (CGM)	Measured at baseline and month 6
Change in mean glucose level	Measured by continuous glucose monitor (CGM)	Measured at baseline and month 6
Change in standard deviation of glucose level	Measured by continuous glucose monitor (CGM)	Measured at baseline and month 6
Change in fat mass, lean mass, visceral fat mass	Measured by DXA	Measured at baseline and month 6
Change in waist circumference	Measured by measuring tape	Measured at baseline and month 6
Change in body mass index (BMI)	Calculated as kg/meter squared	Measured at baseline and month 6
Change in systolic and diastolic blood pressure	Measured by blood pressure cuff	Measured at baseline and month 6
Change in heart rate	Measured by blood pressure cuff	Measured at baseline and month 6
Change in energy and nutrient intake	Measured by 7-day food record	Measured at baseline and month 6
Change in coefficient of variation of glucose level	Measured by continuous glucose monitor (CGM)	Measured at baseline and month 6
Change in absolute body weight	Measured by an electronic scale	Measured at baseline and month 6
Change in dietary adherence	Measured by 7-day food record and adherence log	Measured at baseline and month 6
Change in physical activity (steps/d)	Measured by activity monitor	Measured at baseline and month 6
Change in HbA1c	Measured by ELISA	Measured at baseline and month 6
Change in plasma lipids (total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides)	Measured using enzymatic kits, standardized reagents, and standardsand analyzed using a microplate reader	Measured at baseline and month 6
Adverse events	Measured by adverse events survey and continous glucose monitor (for events of hypoglycemia and hyperglycemia)	Measured at baseline and month 6
Change in insulin dose	Measured by recording total insulin dose, basal insulin dose, and bolus insulin dose	Measured at baseline and month 6

Collaborators and Investigators

• Sponsor: University of Illinois at Chicago
• Investigators: Principal Investigator: Krista Varady, PhD, University of Illinois Chicago

Study record dates

Study Major Dates

• Study Start (Actual): November 20, 2023
• Primary Completion (Actual): September 1, 2025
• Study Completion (Actual): September 1, 2025

Study Registration Dates

• First Submitted: November 11, 2023
• First Submitted That Met QC Criteria: November 11, 2023
• First Posted (Actual): November 18, 2023

Study Record Updates

• Last Update Posted (Actual): March 2, 2026
• Last Update Submitted That Met QC Criteria: February 26, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Endocrine System Diseases; Nutrition Disorders; Metabolic Diseases; Overnutrition; Body Weight; Autoimmune Diseases; Immune System Diseases; Glucose Metabolism Disorders; Diabetes Mellitus; Overweight; Pathological Conditions, Signs and Symptoms; Nutritional and Metabolic Diseases; Signs and Symptoms; Obesity; Diabetes Mellitus, Type 1
• Other Study ID Numbers: 2023-0678

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No