Effect of Whole Fruit on Glycemic Control in Adults With Type 2 Diabetes

NCT ID: NCT03758742

Last Updated: 2025-06-10

Basic Information

• Recruitment Status: COMPLETED
• Clinical Phase: NA
• Total Enrollment: 34 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2019-09-10
• Study Completion Date: 2023-09-05

Brief Summary

Diabetes costs the U.S. healthcare system more than any other disease, and nearly half of Americans will develop either diabetes or prediabetes in their lifetime. It is therefore critical to find new strategies to treat or reverse diabetes.

One such approach is adopting a healthy diet, which can dramatically improve blood sugar levels in adults with type 2 diabetes and even induce diabetes remission. Despite this, not much is known about which food groups are most effective at improving blood sugar levels in patients with diabetes.

Interestingly, of the various food groups, epidemiologic data suggests that whole fruit may be one of the most efficacious at both preventing type 2 diabetes and improving blood sugar in patients with type 2 diabetes. However, few clinical trials have investigated the effects of whole fruit on blood sugar control. This study will therefore be the first to determine the effects of increasing whole fruit as a food group in type 2 diabetes patients. This supervised controlled feeding trial will test whether consuming a diet rich in whole fruit for 12 weeks can improve glycemic control and cardiometabolic health in weight-stable adults with type 2 diabetes. The primary endpoint is glycemic control. Since changes in medication doses can skew the interpretation of glycemic outcomes, glycemic control will be assessed hierarchically (in descending order of importance) using (a) attainment of nondiabetic glycemia without medications (as a proxy for diabetes remission), (b) medication effect scores, (c) mean glucose during an oral glucose tolerance test, and (d) 24-hour mean glucose from continuous glucose monitoring. As secondary aims, this study will also test whether consuming a large amount of fructose in whole food form affects liver fat, pancreatic fat, and cardiovascular disease risk factors.

Conditions

Diabetes Mellitus, Type 2

Study Design

• Allocation Method: NA
• Intervention Model: SINGLE_GROUP
• Primary Study Purpose: TREATMENT
• Blinding Strategy: NONE

Study Groups

High-Fruit Diet

Whole fruit-rich diet (\~50% of calories from whole fruit)

Group Type: EXPERIMENTAL

High-Fruit Diet

Intervention Type: BEHAVIORAL

In this supervised controlled feeding study, participants will consume a diet rich in whole fruit. During the Ramp-Up Phase (Weeks 1-4), participants will gradually increase the amount of whole fruit they consume, eventually reaching 50% of calories from whole fruit. In the Main Phase (Weeks 5-12), participants will consume a whole fruit-rich, eucaloric diet that provides 50% of calories in the form of whole fruit. The non-fruit portion of the diet will be styled as a Mediterranean Diet. Participants will be required to approximately keep their weight stable throughout the intervention.

Interventions

High-Fruit Diet

In this supervised controlled feeding study, participants will consume a diet rich in whole fruit. During the Ramp-Up Phase (Weeks 1-4), participants will gradually increase the amount of whole fruit they consume, eventually reaching 50% of calories from whole fruit. In the Main Phase (Weeks 5-12), participants will consume a whole fruit-rich, eucaloric diet that provides 50% of calories in the form of whole fruit. The non-fruit portion of the diet will be styled as a Mediterranean Diet. Participants will be required to approximately keep their weight stable throughout the intervention.

Intervention Type: BEHAVIORAL

Eligibility Criteria

Inclusion Criteria

• 20-70 years old
• BMI ≤45.0 kg/m^2
• First diagnosed with type 2 diabetes within the past 6 years
• HbA1c between 6.0-9.5%%

Exclusion Criteria

• On insulin
• Diagnosis of diabetes before age 18
• Estimated glomerular filtration rate < 45 ml/min per 1.732 m^2
• Heart attack in the past 6 months or severe or unstable heart failure
• On weight loss medication
• Change in the dosage of a chronic medication that may affect study endpoints within the past 3 months
• Clinically significant laboratory abnormality (e.g. abnormal hemoglobin levels)
• Significant gastrointestinal disease, major gastrointestinal surgery, or gallstones
• Significant cardiovascular, renal, cardiac, liver, lung, adrenal, or nervous system disease that might compromise safety or data validity
• Evidence of cancer (other than non-melanoma skin cancer) within the last 5 years
• Lost or gained more than 5 kg of weight in the past 6 months
• Pregnant, planning to become pregnant in the next 12 months, or breastfeeding
• Major psychiatric condition that would affect the ability to participate in the study
• Not able to eat the provided study meals
• Behavioral factors or circumstances that may impede adhering to the dietary intervention
• Not able to do the MRI/MRS abdominal scan, such as due to claustrophobia, implanted metal objects, or a body girth of 60 cm or greater

• Minimum Eligible Age: 20 Years
• Maximum Eligible Age: 70 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: No

Sponsors

National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)

NIH

Sponsor Role: collaborator

University of Alabama at Birmingham

OTHER

Sponsor Role: lead

Responsible Party

Courtney M Peterson

Associate Professor

Responsibility Role: PRINCIPAL_INVESTIGATOR

Principal Investigators

Courtney M. Peterson, Ph.D.

Role: PRINCIPAL_INVESTIGATOR

University of Alabama at Birmingham

Locations

Department of Nutrition Sciences, University of Alabamam at Birmingham

Birmingham, Alabama, United States

Countries

United States

References

Cobelli C, Dalla Man C, Toffolo G, Basu R, Vella A, Rizza R. The oral minimal model method. Diabetes. 2014 Apr;63(4):1203-13. doi: 10.2337/db13-1198.

Reference Type: BACKGROUND

PMID: 24651807 (View on PubMed)

Hanick CJ, Berg KJ, Garvey WT, Goss AM, Steger FL, Richman JS, Peterson CM. Study protocol, menu design, and rationale for a study testing the effects of a whole fruit-rich diet on glycemic control, liver fat, pancreatic fat, and cardiovascular health in adults with type 2 diabetes. Nutr Res. 2025 Mar;135:82-100. doi: 10.1016/j.nutres.2025.01.008. Epub 2025 Jan 27.

Reference Type: DERIVED

PMID: 39978247 (View on PubMed)

Provided Documents

Document Type: Study Protocol and Statistical Analysis Plan

View Document

Other Identifiers

P30DK079626

Identifier Type: NIH

Identifier Source: secondary_id

View Link

IRB-300001719

Identifier Type: -

Identifier Source: org_study_id