Effects of Acute Exercise in Fasting and Fed States in Individuals With Different Aerobic Fitness Levels

NCT07813403 | Not Yet Recruiting

• 1 other identifier: SBA 26/387
• Study Type: interventional
• Target: 30
• Locations: 1 country
• Sites: 1

Brief Summary

The aim of this study is to investigate the effects of aerobic fitness level, feeding status, and acute exercise on whole-body metabolic fuel utilization and mitochondrial function in peripheral blood mononuclear cells (PBMCs) in healthy young men. The main questions it aims to answer are:

1. 1.Do individuals with high and low aerobic fitness levels differ in fat and carbohydrate oxidation at rest and during exercise following an overnight fast, and do their PBMC mitochondrial responses to acute exercise differ?
2. 2.Does feeding alter fat and carbohydrate oxidation at rest and during exercise compared with the fasted state in individuals with high aerobic fitness?
3. 3.Are PBMC mitochondrial respiration parameters and their exercise-induced changes associated with fat and carbohydrate oxidation during fasted exercise?

Conditions

Physical Fitness; Mitochondrial Function, Bioenergetics; Mitochondria; Energy Metabolism

Keywords

Aerobic Fitness; Metabolic Flexibility; Metabolic Fuel Utilization; Substrate Oxidation; Fasted Exercise; Acute Exercise; Peripheral Blood Mononuclear Cells; Mitochondrial Respiration; Indirect Calorimetry; Maximal Oxygen Uptake; Fat Oxidation; Carbohydrate Oxidation

Outcome Measures

Primary Outcomes (4)

• Change in PBMC Mitochondrial Oxygen Consumption Rate From Pre- to Post-Exercise

  Mitochondrial oxygen consumption rate (OCR) will be measured in peripheral blood mononuclear cells (PBMCs) using a Seahorse XFe96 extracellular flux analyzer. PBMCs will be isolated from venous blood samples collected immediately before and immediately after the fasted 30-minute submaximal cycling test. Pre- to post-exercise changes in OCR will be evaluated between the high and low aerobic fitness groups and examined in relation to whole-body fat and carbohydrate oxidation during exercise.

  Immediately before and immediately after the fasted 30-minute cycling test at 65% of VO2max.

• Change in PBMC Proton Efflux Rate From Pre- to Post-Exercise

  Proton efflux rate (PER) will be measured in peripheral blood mononuclear cells (PBMCs) using a Seahorse XFe96 extracellular flux analyzer. PBMCs will be isolated from venous blood samples collected immediately before and immediately after the fasted 30-minute submaximal cycling test. Pre- to post-exercise changes in PER will be evaluated between the high and low aerobic fitness groups and examined in relation to whole-body substrate oxidation during exercise.

  Immediately before and immediately after the fasted 30-minute cycling test at 65% of VO2max.

• Fat Oxidation Rate During Submaximal Exercise

  Whole-body fat oxidation rate, expressed in grams per minute (g/min), will be calculated using the Frayn stoichiometric equation from oxygen consumption (VO2) and carbon dioxide production (VCO2) measured by indirect calorimetry during 30 minutes of cycling at 65% of the participant's individual VO2max. Fat oxidation will be compared between the high and low aerobic fitness groups under fasted conditions and between the fasted and fed conditions within the high aerobic fitness group.

  During each 30-minute submaximal cycling test performed at 65% of VO2max.

• Carbohydrate Oxidation Rate During Submaximal Exercise

  Whole-body carbohydrate oxidation rate, expressed in grams per minute (g/min), will be calculated using the Frayn stoichiometric equation from oxygen consumption (VO2) and carbon dioxide production (VCO2) measured by indirect calorimetry during 30 minutes of cycling at 65% of the participant's individual VO2max. Carbohydrate oxidation will be compared between the high and low aerobic fitness groups under fasted conditions and between the fasted and fed conditions within the high aerobic fitness group.

  During each 30-minute submaximal cycling test performed at 65% of VO2max.

Secondary Outcomes (4)

• Resting Fat Oxidation Rate

  During the resting metabolic assessment before the fasted and fed exercise conditions.

• Resting Carbohydrate Oxidation Rate

  During the resting metabolic assessment before the fasted and fed exercise conditions.

• PBMC Glycolytic Proton Efflux Rate (glycoPER)

  Immediately before and immediately after the fasted 30-minute cycling test at 65% of VO2max.

• Resting Metabolic Rate

  Before fasted exercise in both groups and 1 hour after the meal before fed exercise in the high-fitness group.

Other Outcomes (2)

• Rating of Perceived Exertion During Submaximal Exercise

  Every 5 minutes during each 30-minute submaximal cycling test.

• Ad Libitum Energy Intake

  During the ad libitum meal provided 1 hour after completion of the fasted exercise test.

Study Arms (2)

High Aerobic Fitness: Fasted and Fed Conditions

EXPERIMENTAL

Participants with a VO2max greater than 55 mL/kg/min who regularly perform endurance training will be assigned to this arm. Participants will complete two repeatability visits under overnight-fasted conditions, including resting metabolic rate measurement followed by 30 minutes of cycling at 65% of VO2max. During the main experimental visit, they will complete the same measurements in the fasted state, with venous blood samples collected immediately before and after exercise. They will subsequently consume an ad libitum meal, and one hour later, resting metabolic rate measurement and the cycling exercise test will be repeated in the fed state.

Behavioral: Acute Moderate-Intensity Cycling Exercise; Other: Ad Libitum Mixed Meal

Low Aerobic Fitness: Fasted Condition

OTHER

Participants with a VO2max lower than 45 mL/kg/min who are sedentary or physically inactive will be assigned to this arm. Participants will complete the fasted experimental condition only. Following an overnight fast, resting metabolic rate will be measured and a venous blood sample will be collected immediately before 30 minutes of cycling at 65% of VO2max. A second venous blood sample will be collected immediately after exercise. Participants in this arm will not complete the repeatability visits or the fed experimental condition.

Behavioral: Acute Moderate-Intensity Cycling Exercise

Interventions

Acute Moderate-Intensity Cycling Exercise BEHAVIORAL

Participants will perform 30 minutes of continuous cycling exercise on a cycle ergometer at an intensity corresponding to 65% of their individual maximal oxygen uptake (VO2max). Both aerobic fitness groups will complete the exercise following an overnight fast. Participants in the high aerobic fitness group will also repeat the exercise one hour after consuming an ad libitum meal. Respiratory gas exchange will be measured throughout exercise to calculate fat and carbohydrate oxidation, and rating of perceived exertion will be recorded every five minutes using the Borg 6-20 scale.

High Aerobic Fitness: Fasted and Fed Conditions; Low Aerobic Fitness: Fasted Condition

Ad Libitum Mixed Meal OTHER

One hour after completing the fasted exercise test, participants in the high aerobic fitness group will be provided with an ad libitum mixed meal consisting of pasta and meatballs and will be allowed to eat until comfortably full. One hour after the meal, resting metabolic rate measurement and the 30-minute cycling exercise test at 65% of VO2max will be repeated under the fed condition. No blood samples will be collected during the fed condition.

High Aerobic Fitness: Fasted and Fed Conditions

Eligibility Criteria

• Age: 18 Years - 25 Years
• Sex: male
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• Healthy male volunteers aged 18-25 years
• Body mass index between 18.5 and 24.9 kg/m²
• Residing on the Hacettepe University Beytepe Campus
• Eligibility for one of the following aerobic fitness groups
• High aerobic fitness group: maximal oxygen uptake (VO2max) greater than 55 mL/kg/min and regular participation in endurance training.
• Low aerobic fitness group: VO2max lower than 45 mL/kg/min and sedentary or not regularly physically active

You may not qualify if:

• Current smoking
• Regular or excessive alcohol consumption
• Any musculoskeletal condition that may limit or prevent exercise
• Allergy to any of the foods provided as part of the study meal
• Currently following a weight-loss or other restrictive diet

Sponsors & Collaborators

• Hacettepe University: lead

Study Sites (1)

Hacettepe University, Faculty of Sport Sciences

Ankara, Ankara, 06800, Turkey (Türkiye)

Location

Related Publications (6)

• Hedges CP, Woodhead JST, Wang HW, Mitchell CJ, Cameron-Smith D, Hickey AJR, Merry TL. Peripheral blood mononuclear cells do not reflect skeletal muscle mitochondrial function or adaptation to high-intensity interval training in healthy young men. J Appl Physiol (1985). 2019 Feb 1;126(2):454-461. doi: 10.1152/japplphysiol.00777.2018. Epub 2018 Dec 20.

  PMID: 30571281 BACKGROUND

• Mookerjee SA, Goncalves RLS, Gerencser AA, Nicholls DG, Brand MD. The contributions of respiration and glycolysis to extracellular acid production. Biochim Biophys Acta. 2015 Feb;1847(2):171-181. doi: 10.1016/j.bbabio.2014.10.005. Epub 2014 Oct 27.

  PMID: 25449966 BACKGROUND

• Atakan MM, Guzel Y, Bulut S, Kosar SN, McConell GK, Turnagol HH. Six high-intensity interval training sessions over 5 days increases maximal oxygen uptake, endurance capacity, and sub-maximal exercise fat oxidation as much as 6 high-intensity interval training sessions over 2 weeks. J Sport Health Sci. 2021 Jul;10(4):478-487. doi: 10.1016/j.jshs.2020.06.008. Epub 2020 Jun 18.

  PMID: 32565243 BACKGROUND

• Theall B, Stampley J, Cho E, Granger J, Johannsen NM, Irving BA, Spielmann G. Impact of acute exercise on peripheral blood mononuclear cells nutrient sensing and mitochondrial oxidative capacity in healthy young adults. Physiol Rep. 2021 Dec;9(23):e15147. doi: 10.14814/phy2.15147.

  PMID: 34889067 BACKGROUND

• Liepinsh E, Makarova E, Plakane L, Konrade I, Liepins K, Videja M, Sevostjanovs E, Grinberga S, Makrecka-Kuka M, Dambrova M. Low-intensity exercise stimulates bioenergetics and increases fat oxidation in mitochondria of blood mononuclear cells from sedentary adults. Physiol Rep. 2020 Jun;8(12):e14489. doi: 10.14814/phy2.14489.

  PMID: 32562386 BACKGROUND

• Janssen JJE, Lagerwaard B, Porbahaie M, Nieuwenhuizen AG, Savelkoul HFJ, van Neerven RJJ, Keijer J, de Boer VCJ. Extracellular flux analyses reveal differences in mitochondrial PBMC metabolism between high-fit and low-fit females. Am J Physiol Endocrinol Metab. 2022 Feb 1;322(2):E141-E153. doi: 10.1152/ajpendo.00365.2021. Epub 2022 Jan 10.

  PMID: 35001658 BACKGROUND

Study Officials

• Süleyman BULUT, PhD

  Hacettepe University, Faculty of Sport Sciences

  PRINCIPAL INVESTIGATOR

• Muhammed M ATAKAN, PhD

  Hacettepe University, Faculty of Sport Sciences

  PRINCIPAL INVESTIGATOR

Central Study Contacts

Burcu ÖZALP, MSc student

CONTACT

+905539286638; burcu.ozalp@hacettepe.edu.tr

Süleyman BULUT, PhD

CONTACT

+903122976890; slmbulut@hacettepe.edu.tr

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: NON RANDOMIZED
• Masking: NONE
• Purpose: BASIC SCIENCE
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Assistant Professor

Model Details: Participants will be non-randomly classified into two parallel groups according to measured maximal oxygen uptake (VO2max) and habitual training status. The high aerobic fitness group will complete repeated fasted assessments and a main experimental visit including fasted and fed exercise conditions in a fixed order. The low aerobic fitness group will complete the fasted experimental condition only. Both groups will perform 30 minutes of cycling exercise at 65% of their individual VO2max.

Study Record Dates

• First Submitted: September 4, 2026
• First Posted: September 10, 2026
• Study Start (Estimated): November 15, 2026
• Primary Completion (Estimated): November 15, 2027
• Study Completion (Estimated): December 15, 2027
• Last Updated: September 10, 2026

Record last verified: 2026-09

Data Sharing

• IPD Sharing: Will not share

Locations

TU (1)