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Completed

NCT Number: NCT07503990

Effects of Food Intake Sequence on Substrate Utilisation and Endurance Performance

The goal of this clinical trial is to understand how consuming a pre-exercise meal in different food intake sequences affects substrate utilisation and endurance exercise performance in healthy trained athletes. Specifically, the main questions it aims to answer are:

* Does consuming the pre-exercise meal in different food intake sequences alter the whole-body utilisation of fat and CHO at rest and during prolonged exercise at moderate to heavy intensities? * Does consuming the pre-execise meal in different food intake sequences alter time-trial performance? * Does consuming the pre-exercise meal in different food intake sequences alter other metabolic and physiological responses before, during or after exercise (i.e., blood glucose, blood lactate, heart rate (HR), ratings of perceived exertion (RPE), appetite)?

To address these questions, researchers will compare eating the dietary sources of rapidly absorbed CHO at the end (CHO-last meal pattern) or at the start (CHO-first meal pattern) of a standardised pre-exercise meal, in a randomised, counterbalanced, crossover design. Two hours after starting the pre-exercise meal, participants will perform a 60-min submaximal test on a cycling ergometer at two different intensities (30 min at 90% of the ventilatory threshold (VT) 1 and 30 min at 50% VT1-VT2), followed by a 10-km cycling time trial (TT).

In the screening visit participants will:

* Be screened for cardiometabolic conditions * Perform an 8-12-min graded exercise test to determine their maximal pulmonary oxygen uptake (VO2max) and non-invasive submaximal anchors of performance (VT 1 and VT 2) * Be familiarised to the experimental procedures

In experimental visits participants will:

* Follow guidelines pertaining to dietary intake, exercise and sleep in the previous 24 hours * Have a standardised test meal in either the CHO-last or CHO-first food intake sequence * Have 3 drops of capillary blood (0,9 µL in total) collected to measure glucose and lactate pre-meal, 15, 30, 45, 60, 90 and 120 min post-meal, every 15 min during submaximal exercise and post-TT * Breathe into an indirect calorimetry mask for 5 min pre-meal, 15, 30, 45, 60, 90 and 120 min post-meal, every 15 min during submaximal exercise and post-TT * Wear a HR monitor continuously during submaximal exercise and the TT * Rate their appetite on visual analogue scales pre-meal, 15, 30, 45, 60, 90 and 120 min post-meal, and 30 min post-TT * Rate their perceived exertion on RPE scales every 15 min during submaximal exercise, post-TT and 30 min post-TT.

Data will be compared within-participant between food intake sequences using linear mixed-effects models with random intercepts, to account for repeated measurements, interindividual variability, and potential missing data.

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Key information

Age range

18 year–64 year

Sex eligibility

Male

Study type

Interventional

Phase

Not applicable

Primary location

Cidade do Futebol

Lisbon, Oeiras, 1495-433, Portugal

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Adult (18-64 years old)
  • Men
  • Endurance-trained athletes (meeting training and performance caliber criteria ≥Tier 2; McKay et al., 2022)
  • Healthy (meeting the exclusion criteria for medical conditions)
  • Normal glucose tolerant according to the latest criteria established by the American Diabetes Association (2024): HbA1c <5.7%, fasting plasma glucose <5.6 mmol/L (100 mg/dL) or 2-h plasma glucose <7.8 mmol/L (140 mg/dL) during a 75-g OGTT
  • Able and willing to provide informed consent and safely comply with study procedures

Exclusion criteria

  • Any medical condition or behaviour deemed either to pose undue personal risk to the participant or introduce bias into the experiment (e.g. cardiovascular disease; alcohol or substance abuse; any condition affecting the glucose or lipid metabolism, reviewed on a case by case basis)
  • Any reported medication or supplementation that may interfere with the glucose metabolism (e.g., acarbose, insulin, metformin, semaglutide, thiazolidinediones, sulfonylureas, corticosteroids, thiazide diuretics) or lipid metabolism (e.g., statins, nicotinic acid, colestyramine anhydrous, ezetimibe, fibrates, L-carnitine). Other medication and supplementation will be reviewed on a case by case basis.
  • Known food allergy, intolerance or hypersensitivity to any of the test meal ingredients
  • Recent change in body mass (± 2 kg in the last 2 months)
  • Smoking

Treatment and study plan

Carbohydrate-last meal pattern

Other

Skyr yoghurt, whey protein and almonds over ~5 min, immediately followed by white bread, strawberry jam, banana and pulp-free orange juice over ~10 min.

Other names: CHO-last, CL

Carbohydrate-first meal pattern

Other

White bread, strawberry jam, banana and pulp-free orange juice over ~10 min, immediately followed by skyr yoghurt, whey protein and almonds over ~5 min.

Other names: CHO-first, CF

Primary outcomes

  1. Whole-body fat oxidation

    Time frame: Every 15 minutes post-meal (0-120 minutes), every 15 minutes throughout the subsequent standardised exercise protocol (120-180 minutes)

    Difference between CHO-last and CHO-first meal patterns in the whole-body fat oxidation rate (g/min) over time adjusted for baseline, measured by indirect calorimetry.

  2. Time-trial performance

    Time frame: Immediately upon completion of the time trial subsequent to the post-meal resting period (0-120 minutes) and standardised exercise protocol (120-180 minutes)

    Difference between CHO-last and CHO-first meal patterns in the time to complete (min:sec) a 10-km cycling TT, assessed using a validated cycle ergometer.

Secondary outcomes

  1. Time-trial power output

    Time frame: Immediately upon completion of the time trial subsequent to the post-meal resting period (0-120 minutes) and standardised exercise protocol (120-180 minutes)

    Difference between CHO-last and CHO-first meal patterns in the average power output (W) during a 10-km cycling TT, assessed using a validated cycle ergometer.

  2. Whole-body CHO oxidation

    Time frame: Every 15 minutes post-meal (0-120 minutes), every 15 minutes throughout the subsequent standardised exercise protocol (120-180 minutes)

    Difference between CHO-last and CHO-first meal patterns in the whole-body CHO oxidation rate (g/min) over time adjusted for baseline, measured by indirect calorimetry.

  3. Respiratory exchange ratio (RER)

    Time frame: Every 15 minutes post-meal (0-120 minutes), every 15 minutes throughout the subsequent standardised exercise protocol (120-180 minutes)

    Difference between CHO-last and CHO-first meal patterns in the RER over time adjusted for baseline, measured by indirect calorimetry.

  4. Energy expenditure

    Time frame: Every 15 minutes post-meal (0-120 minutes), every 15 minutes throughout the subsequent standardised exercise protocol (120-180 minutes)

    Difference between CHO-last and CHO-first meal patterns in the energy expenditure rate (kcal/min) over time adjusted for baseline, measured by indirect calorimetry.

  5. Blood glucose concentrations

    Time frame: Every 15 minutes post-meal in the first hour (0-60 min), every 30 minutes in the second hour (60-120 min), every 15 minutes throughout the standardised exercise protocol (120-180 min) and immediately upon completion of the subsequent time trial

    Difference between CHO-last and CHO-first meal patterns in the capillary blood glucose concentrations (mmol/L) over time adjusted for baseline, measured by a validated glucometer.

  6. Blood lactate concentrations

    Time frame: Every 15 minutes post-meal in the first hour (0-60 min), every 30 minutes in the second hour (60-120 min), every 15 minutes throughout the standardised exercise protocol (120-180 min) and immediately upon completion of the subsequent time trial

    Difference between CHO-last and CHO-first meal patterns in the capillary blood lactate concentrations (mmol/L) over time adjusted for baseline, measured by a validated lactate meter.

  7. Heart Rate

    Time frame: Continuously throughout the standardised exercise protocol (120-180 minutes) and subsequent time trial

    Difference between CHO-last and CHO-first meal patterns in the heart rate (bpm) over time adjusted for baseline, assessed as 15-minute averages during exercise using a validated heart rate monitor.

  8. Ratings of perceived exertion (RPE)

    Time frame: Every 15 minutes during the standardised exercise protocol (120-180 minutes), immediately upon completion of the subsequent time trial, 30 minutes after completion of the time trial

    Difference between CHO-last and CHO-first meal patterns in the absolute RPE over time, assessed during and after exercise using the validated modified Borg's 0-10 scale.

  9. Subjective appetite ratings

    Time frame: Every 15 minutes post-meal in the first hour (0-60 minutes), every 30 minutes in the second hour (60-120 minutes), and 30 minutes after completion of the time trial

    Difference between CHO-last and CHO-first meal patterns in the appetite ratings (mm) over time adjusted for baseline, assessed at rest and after exercise using validated 100-mm visual analogue scales.

Sponsors and collaborators

Lead sponsor

Universidade do Porto

Other

Collaborators

  • Fundação para a Ciência e a Tecnologia
  • Portuguese Football Federation

Registry information

Official study title

Effects of Manipulating Food Intake Sequence in the Pre-exercise Meal on Substrate Utilisation and Endurance Performance in Athletes

Important dates

Study start
2026
Primary completion
2026
Study completion
2026
First posted
Mar 31, 2026
Registry last updated
Jun 10, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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