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

Abstract

Dietary interventions such as very-low-calorie diets and low-carbohydrate diets can improve glycemic control and even induce type 2 diabetes (T2D) remission. However, less is known about the effects of carbohydrate-rich whole foods, such as whole fruit, in people with T2D. Therefore, the aim of this pilot study is to investigate the effects of a whole fruit-rich diet on glycemic control, ectopic fat, and cardiovascular risk factors in adults with T2D. In this pilot study, sixteen adults aged 20 to 70 years with insulin-independent T2D for ≤6 years will complete a 12-week controlled-feeding intervention while maintaining their weight. During the ramp-up phase (weeks 1-4), participants progressively consume more whole fruit. During weeks 5 to 12, participants eat a fruit-rich Mediterranean diet providing 50% of calories as whole fruit (∼16.4 servings/day). All outcomes are measured at weeks 0, 4, and 12. The primary outcome is glycemic control, assessed hierarchically by whether participants achieve nondiabetic glucose concentrations without antihyperglycemic medications; the total dose of antihyperglycemic medications; mean glucose during a three-hour oral glucose tolerance test; and mean 24-hour glucose from continuous glucose monitoring. Secondary outcomes include intrahepatic lipid, pancreatic fat, blood pressure, heart rate, and serum lipids. We hypothesize that a fruit-rich diet will improve glycemic control, reduce the need for antihyperglycemic medications, decrease ectopic fat, and improve cardiovascular risk factors. This novel study will help determine the effects of a whole fruit-rich diet on glycemic control and liver fat and whether diabetes remission may be possible without losing weight. This study was registered at ClinicalTrials.gov (NCT03758742).