Inter-day Reliability of the Oral Glucose Tolerance Test Using Indirect Calorimetry

The main aim of this study is to determine the inter-day reliability, by using indirect calorimetry, of the post-prandial macronutrient oxidation and energy expenditure after consuming oral glucose load solution.

The maintenance of blood glucose concentrations and the oxidation of carbohydrate after consuming carbohydrate is related with a low risk of mortality and morbidity from cardiometabolic diseases. The oral glucose tolerance test is a diagnostic test widely used in the clinical field. However, its inter-day reliability has not been deeply studied. Therefore, it is of clinical interest to study the inter-day reliability of the diagnostic test oral glucose tolerance test using indirect calorimetry and monitoring the response of the glucose levels. 20 young adults will undergo two trials visit with 7 days of separation between conditions. Each evaluation day will conform to the following tests: Basal metabolic rate assessment through indirect calorimetry. Basal heart rate variability through heart rate monitor. Intake of the corresponding glucose load solution. Postprandial nutrient oxidation and energy expenditure assessment through indirect calorimetry Glucose monitoring through Glucose meter.

Participants will undergo two trials visit (with a week of separation). During the visits they will ingest an oral glucose load solution (oral glucose tolerance test) and gas exchange will be measured over the following 3-hours. The glucose levels will be monitored through a Glucose meter in different time frames.

Participants will ingest 75g anhydrous glucose dissolved in a volume of 200mL of water (NUTER.TEC GLUCOS, Subra, Toulouse, France).

• Reliability of the O2 and CO2 metabolic cart sensors by pure gases infusions using a high-precision mass-flow controllers

o Inter-day reliability of gas composition (O2 and CO2) measurement by the Omnical® assessed by comparison with a high-precision mass-flow controllers.

Inclusion Criteria: Healthy male or female Ages 18-30 years BMI: 18-27.5 kg/m2 Stable weight over the last 3 months (body weight changes<35kg) Participant must be capable and willing to provide consent, understand exclusion criteria, instructions and protocols. Exclusion Criteria: History of cardiovascular disease Diabetes or hypertension Pregnant, planning to become pregnant, or breastfeeding Have been treated previously or during the study period with prescription drugs: antihypertensive, lipid lowering, acid uric lowering, glucose lowering, beta blockers or any drug that under the investigator's judged could influence the results. Any non-controlled medical condition which could influence results or could be worsened by the participation in the study. Claustrophobia Needle phobia Are deemed unsuitable by the investigator for any other reason, that prevent data collection.

Alcantara JMA, Sanchez-Delgado G, Jurado-Fasoli L, Galgani JE, Labayen I, Ruiz JR. Reproducibility of the energy metabolism response to an oral glucose tolerance test: influence of a postcalorimetric correction procedure. Eur J Nutr. 2023 Feb;62(1):351-361. doi: 10.1007/s00394-022-02986-w. Epub 2022 Aug 25.