The RepEAT Study: Individual Differences in Postprandial Glucose Responses and the Relation With Diet and Phenotype

Postprandial glucose responses are related to an increased risk of developing cardiometabolic diseases. Existing research recognizes the presence of inter-individual variation in postprandial glucose responses to the same meal or food product. However, the role of diet and phenotype in postprandial glucose responses is unclear.

The primary objective of this study is to determine the variation in postprandial glucose responses to the same meals/food products and how this relates to the variation in postprandial glucose responses over a 9-week fully controlled dietary intervention within and between individuals. Our secondary objectives are to investigate the difference between postprandial glucose responses to original products and postprandial glucose responses to reformulated products, and to examine the relation between postprandial glucose responses and short-term well-being. In addition, we aim to study the relation between variation in postprandial glucose and phenotype, including immune function, cognitive performance, and microbiota composition.

63 apparently healthy men and women with a BMI of 25-40 kg/m2, aged 45-75 years will be included in the study, comprising a characterization period of 3 weeks and a completely controlled dietary intervention of 9 weeks. During these 9 weeks, glucose will be continuously monitored to measure postprandial glucose responses to standard foods/meals.

There are minor risks for the research subjects of this study. Research subjects will invest approximately 85 hours in the study. During the characterization week, subjects will visit the Wageningen University 3 times and Hospital Gelderse Vallei (Ede, The Netherlands) once. During the controlled dietary intervention, subjects will visit the Wageningen University 2-3 times a week.

Postprandial glucose responses are related to an increased risk of developing cardiometabolic diseases. Existing research recognizes the presence of inter-individual variation in postprandial glucose responses to the same meal or food product. However, the role of diet, i.e. the other consumed food products and meals, and phenotype in postprandial glucose responses is unclear. A repetitive design and a standardized diet are necessary to determine the variation in postprandial glucose responses to a meal or food product irrespective of the diet.

The primary objective of this study is to determine the variation in postprandial glucose responses to the same meals/food products and how this relates to the variation in postprandial glucose responses over a 9-week fully controlled dietary intervention within and between individuals. Our secondary objectives are to investigate the difference between postprandial glucose responses to original products and postprandial glucose responses to reformulated products, and to examine the relation between postprandial glucose responses and short-term well-being. In addition, we aim to study the relation between variation in postprandial glucose and phenotype, including immune function, cognitive performance, and microbiota composition.

The study population consists of 63 apparently healthy men and women with a BMI of 25-40 kg/m2, aged 45-75 years, and who are weight stable (± \<3 kg) for at least three months prior to inclusion.

The study comprises a characterization period of three weeks, followed by a fully controlled dietary intervention trial of nine weeks. In the characterization period, the phenotype of participants will be determined by measures on anthropometrics, immune function, oxidative stress, advanced glycation end-products, cognitive performance, microbiota and gut health, amylase, genetics, and circulating metabolites. The dietary intervention consists of three repetitive rounds of three weeks, in which we test food products in a cross-over setting. Participants will consume test products that fall in the same food category, but differ in glycaemic index/carbohydrate content. Part of these products is provided by industrial partners, of which the original products are reformulated to be reduced in glycaemic index/carbohydrate content. During the 9-week dietary intervention all foods are provided, giving us a complete and detailed picture of food and nutrient intake during this period. The standardized diet follows the average consumption pattern of the study population. Throughout the intervention, interstitial glucose concentrations will be measured using continuous glucose monitoring (CGM) and physical activity will be monitored with an accelerometer.

This study is related to a broad general population. There are minor risks for the research subjects of this study. Placing a continuous glucose sensor generally does not cause pain, but could result in the loss of a drop of blood, or slight skin irritation after wearing. Blood sampling will be performed via a cannula or venapunction and the insertion can be a bit painful and may cause a bruise. During the characterization period, in total 215 mL of blood will be collected in a 3-week timespan. In the following 9 weeks 108 mL, and at the end of the intervention 34 mL blood will be collected. Research subjects will invest approximately 85 hours in the study. During the characterization week, subjects will visit the Wageningen University 3 times and Hospital Gelderse Vallei (Ede, The Netherlands) once. During the controlled dietary intervention, subjects will visit the Wageningen University 2-3 times a week.

Eligibility Criteria:
Inclusion Criteria:

* Apparently healthy men and women
* BMI of 25 - 40 kg/m2
* Age 45-75 years
* Weight stable (± \<3 kg) for at least two months prior to inclusion

Exclusion Criteria:

* Diagnosed with type 1 or type 2 diabetes
* Diseases or prior surgeries affecting the stomach, liver, or intestines
* Food allergies/intolerances for products used in the study design
* Receiving medication or supplements interfering with glucose metabolism (as judged by our research physician)
* Regular use of medication interfering with immune function (e.g. corticosteroids, immune blockers, as judged by our research physician)
* Donated blood within 2 months prior to the screening
* Anaemia defined as Hb concentrations \<8.5 mmol/L for men and \<7.5 mmol/L for women
* Veins not suitable for venflon needle
* Allergy/intolerance to medical skin adhesives
* Dietary habits interfering with the study design (e.g. vegetarian, vegan, ketogenic diet)
* Intention to change the intensity of exercise during the study period
* Current smokers
* Alcohol intake ≥14 alcoholic beverages per week (women) or ≥21 alcoholic beverages per week (men)
* Being pregnant or lactating
* Use of soft and/or hard drugs
* Unable/unwilling to download a research application on the mobile phone
* Participation in another study that involves an intervention within two months prior to the intervention
* Working at the division of Human Nutrition and Health of Wageningen University and Research or the Food, Health and Consumer research group of Wageningen University and Biobased Research