Low-calorie Diet in Isolated Impaired Fasting Glucose

Effect of Dietary Energy Restriction on Reversing Isolated Impaired Fasting Glucose: A Proof of Concept Study

This study aims to evaluate the preliminary efficacy of a low-calorie diet (LCD) intervention in addressing the underlying pathophysiological abnormalities and improving fasting hyperglycemia among individuals with isolated impaired fasting glucose (i-IFG). Additionally, it seeks to assess the feasibility and acceptability of the LCD intervention.

Study Overview

• Status: Not yet recruiting
• Conditions: Isolated Impaired Fasting Glucose
• Intervention / Treatment: Behavioral: Low-calorie diet; Behavioral: Routine dietary and physical activity habits

Detailed Description

This proof-of-concept randomized controlled trial (RCT) will enroll 34 individuals aged 35-65 years with overweight or obesity and isolated impaired fasting glucose. Intervention participants will adhere to an 8-week low-calorie dietary (LCD) regimen (~1,320 kcal/day) comprising specific macronutrient proportions (55% carbohydrate, 13% fat, 25% protein, and 2% fiber). Control participants will maintain their habitual dietary habits and physical activity levels. Primary outcomes at 8 weeks include between-group changes in weight, fasting plasma glucose, indices of ß-cell function and hepatic insulin resistance, and alanine aminotransferase levels. Secondary outcomes are feasibility metrics (response rate, screening yield, enrollment rate, intervention compliance, cost, staff time, and retention rate) and intervention acceptability. Qualitative research will explore facilitators, barriers, acceptability, satisfaction, and participant experiences with the LCD intervention.

• Study Type: Interventional
• Enrollment (Estimated): 34
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Sathish Thirunavukkarasu, PhD; Phone Number: (404) 778-3771; Email: sathish.thirunavukkarasu@emory.edu

Study Locations

• United States
  • Georgia
    • Atlanta, Georgia, United States, 30322
      • Georgia Clinical & Translational Science Alliance (CTSA) Clinical Research Centers (GCRCs)

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

1. Aged 35 to 65 years
2. Overweight (body mass index (BMI) ≥25 to <29 kg/m² or ≥23 to <29 kg/m² if Asian descent) or Obese (BMI ≥30 kg/m²)
3. Physically inactive (<150 minutes per week of moderate-intensity physical activity or <75 minutes per week of vigorous-intensity physical activity)
4. Prediabetes diagnosis or score ≥5 on the American Diabetes Association (ADA) risk tool

Exclusion Criteria:

1. Diagnosed with type 1 or type 2 diabetes
2. Cardiovascular disease (myocardial infarction, stroke, angina, heart failure, or other cardiac conditions)
3. Chronic kidney disease
4. Chronic liver disease (e.g., cirrhosis)
5. Cancers
6. Acute inflammatory bowel disease, irritable bowel syndrome, celiac disease, chronic pancreatitis, or other disorders potentially causing malabsorption
7. Food allergies
8. Participation in weight loss programs in the past six months
9. Currently following a specific diet (e.g., ketogenic diet, Mediterranean diet)
10. Participation in any exercise programs in the past six months
11. Currently taking weight-loss medications or drugs known to affect glycemia (steroids and antipsychotics)
12. Previous bariatric surgery or plan to have bariatric surgery during the study period
13. Planning to relocate during the study period
14. Intending to fast during the study period for religious or other reasons
15. Pregnancy or planning to become pregnant during the study period
16. Breastfeeding
17. Non-English speaker

Study Plan

How is the study designed?

Design Details

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

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Low-calorie diet; Participants following a low-calorie diet (LCD) consisting of approximately 1,300 kcal/day (37% carbohydrates, 25% protein, 39% fat, and 7 g of fiber per meal) over an eight-week period.	Behavioral: Low-calorie diet; The low-calorie diet consists of approximately 1,300 kcal/day (37% carbohydrates, 25% protein, 39% fat, and 7 g of fiber per meal) over an eight-week period. Participants receive weekly pre-prepared meals from Trifecta Nutrition (Trifecta Inc. California, USA) with options for breakfast, lunch, and dinner, meticulously crafted by certified dieticians and expert chefs. Participants are encouraged to consume 1-2 liters of water daily and maintain their habitual physical activity levels.; Other Names: Dietary energy restriction
Active Comparator: Routine dietary and physical activity habits; Control participants are asked to maintain their routine dietary and physical activity habits.	Behavioral: Routine dietary and physical activity habits; Participants are asked to maintain their habitual dietary and physical activity habits for the 8-week study period.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Response rate	Response rate is defined as the proportion of individuals responding to the invitation sent via the Epic database.	Baseline
Screening yield	Screening yield: Proportion of screened individuals meeting eligibility criteria.	Baseline
Enrollment rate	Enrollment rate: Proportion of eligible individuals who enroll in the study.	Baseline
Resource utilization	Resource utilization: Assessment of expenditures and staff time.	Throughout the study period, an average of 10 weeks
Retention rate	Retention rate: Proportion of enrolled participants who complete the study.	4 and 8 weeks
Intervention acceptability	Intervention acceptability will be assessed using the Theoretical Framework of Acceptability questionnaire. Scores range from 7 to 35. Higher scores indicate better acceptability among participants.	4 and 8 weeks
Feasibility of intervention	Will be assessed using the Feasibility of Intervention Measure questionnaire. Scores range from 4 to 20. Higher scores indicate better feasibility among participants.	4 and 8 weeks
Intervention appropriateness	Will be assessed with the Intervention Appropriateness Measure questionnaire. Scores range from 4 to 20. Higher scores indicate better appropriateness among participants.	4 and 8 weeks
Facilitators, barriers, acceptability, satisfaction, and participant experiences with the the intervention	Qualitative in-depth interviews	4 and 8 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Fasting plasma glucose in mg/dl	Will be analyzed by enzymatic assays	4 and 8 weeks
Alanine aminotransferase (liver enzyme) in U/L	Will be analyzed with colorimetric assays	4 and 8 weeks
Weight in kg	Weight will be measured using a digital weighing scale with an accuracy to the nearest 0.1 kg	4 and 8 weeks
Indices of ß-cell function	Will be assessed using the insulinogenic index (IGI)	4 and 8 weeks
ß-cell function assessed by Oral Disposition Index (DI(O))	Will be assessed using the Oral Disposition Index (DI(O))	4 and 8 weeks
ß-cell function assessed by Homeostatic Model Assessment of ß-cell Function (HOMA-B)	Will be assessed using the Homeostatic Model Assessment of ß-cell Function (HOMA-B)	4 and 8 weeks
Indices of hepatic insulin resistance	Will be assessed using the Hepatic Insulin Resistance Index (HIRI)	4 and 8 weeks

Collaborators and Investigators

• Sponsor: Emory University
• Investigators: Principal Investigator: Sathish Thirunavukkarasu, PhD, Emory University

Study record dates

Study Major Dates

• Study Start (Estimated): June 1, 2026
• Primary Completion (Estimated): December 30, 2026
• Study Completion (Estimated): December 30, 2026

Study Registration Dates

• First Submitted: May 31, 2024
• First Submitted That Met QC Criteria: June 8, 2024
• First Posted (Actual): June 10, 2024

Study Record Updates

• Last Update Posted (Estimated): January 12, 2026
• Last Update Submitted That Met QC Criteria: January 8, 2026
• Last Verified: January 1, 2026

More Information

Terms related to this study

• Keywords: Obesity; Prediabetes; Overweight; Low-calorie diet; Fasting hyperglycemia
• Additional Relevant MeSH Terms: Endocrine System Diseases; Nutrition Disorders; Metabolic Diseases; Overnutrition; Body Weight; Glucose Metabolism Disorders; Diabetes Mellitus; Pathological Conditions, Signs and Symptoms; Nutritional and Metabolic Diseases; Signs and Symptoms; Overweight; Obesity; Prediabetic State; Therapeutics; Diet, Food, and Nutrition; Physiological Phenomena; Nutritional Physiological Phenomena; Diet Therapy; Nutrition Therapy; Diet; Energy Intake; Caloric Restriction
• Other Study ID Numbers: STUDY00007848

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