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NCT Number: NCT07402902

Caffeine Strategies and Fat Oxidation

The goal of this clinical trial is to learn if different forms of caffeine ingestion can influence fat oxidation during submaximal cycling exercise. The study will recruit healthy adults, both men and women, aged 18 to 50, who regularly perform aerobic exercise. The main questions it aims to answer are:

* Does caffeine increase fat oxidation during one hour of cycling at the Fatmax intensity? * Do different forms of caffeine ingestion (capsule, coffee, chewing gum, or mouth rinse) differ in their effect on fat oxidation? * Do these caffeine forms alter total energy expenditure, cardiorespiratory response, or perceived exertion during exercise? * Are there differences in the occurrence or severity of side effects between caffeine administration methods?

Researchers will compare each caffeine form to its corresponding placebo to determine their effects on fat oxidation and other physiological outcomes.

Participants will:

* Attend a pre-experimental session to determine their Fatmax intensity and VO₂max using an incremental cycling test * Perform eight experimental sessions, each consisting of one hour of cycling at Fatmax intensity * Receive caffeine or placebo via capsules, coffee, chewing gum, or mouth rinse according to a randomized, double-blind, crossover design * Be monitored for fat and carbohydrate oxidation, total energy expenditure, heart rate, and perceived exertion during exercise * Report any side effects immediately after the session and 24 hours later using a structured questionnaire

All sessions will be conducted under controlled laboratory conditions with standardized protocols to ensure safety and reliable measurements.

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Key information

Conditions

Fat Metabolism Behavior Caffeine Cycling Ergogenics Exercise Motor Activity

Age range

18 year–50 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Estadio Raúl González Blanco, Camino del Molino 5

Fuenlabrada, Madrid, 28942, Spain

Who can participate

Healthy volunteers accepted: Yes

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

Inclusion criteria

  • Healthy men and women aged 18-50 years
  • Regular aerobic exercise at least 1 hour per day, 2 days per week
  • Provide written informed consent

Exclusion criteria

  • Smoking
  • Use of medication or ergogenic supplements during the study period
  • Caffeine intolerance or allergy
  • Cardiopulmonary or musculoskeletal disorders
  • Use of oral contraceptives in female participants

Treatment and study plan

Caffeine (Guinama Anhydrous Powder)

Drug

3 mg/kg of anhydrous caffeine powder (Guinama, Spain) administered in an opaque capsule 60 min before exercise.

Caffeine (Nescafé Classic Coffee)

Dietary Supplement

3 mg/kg of caffeine via Nescafé Classic (Nestlé, Switzerland) dissolved in 250 mL of water 60 min before exercise.

Caffeine (Kafewake Gum)

Dietary Supplement

3 mg/kg of caffeine via Kafewake gum (Arafarma group, Spain), chewed for 10 min before exercise.

Caffeine Mouth Rinse Solution

Other

3 mg/kg of caffeine (Nescafé Classic) dissolved in 25 mL of water for a 20-second rinse before exercise.

Placebo (Cellulose Capsule)

Other

Opaque capsule containing cellulose powder, matching caffeine capsules, taken 60 min before exercise.

Placebo (Decaffeinated Coffee)

Other

Decaffeinated Nescafé (Nestlé, Switzerland) in 250 mL of water, matching caffeinated coffee, taken 60 min before.

Placebo (Non-caffeine Gum)

Other

Kafewake Non-caffeinated gum (Arafarma group, Spain) with identical taste and texture, chewed for 10 min before.

Placebo Mouth Rinse Solution

Other

Decaffeinated Nescafé in 25 mL of water for a 20-second rinse immediately before exercise.

Primary outcomes

  1. Rate of fat oxidation during submaximal cycling exercise at Fatmax intensity

    Time frame: 1 hour per experimental session

    Continuous measurement of fat oxidation using indirect calorimetry during 1-hour cycling at Fatmax intensity. Calculated from respiratory gas exchange (VO₂ and VCO₂) using Frayn's equations. Unit of Measure: grams per minute (g/min).

Secondary outcomes

  1. Rate of carbohydrate oxidation during submaximal cycling exercise at Fatmax intensity

    Time frame: 1 hour per experimental session

    Continuous measurement of carbohydrate oxidation using indirect calorimetry during 1-hour cycling at Fatmax intensity. Calculated from respiratory gas exchange (VO₂ and VCO₂) using Frayn's equations. Unit of Measure: grams per minute (g/min).

  2. Total energy expenditure during exercise

    Time frame: 1 hour per experimental session

    Estimated from indirect calorimetry data using Brouwer's equation, recorded continuously during 1-hour cycling at Fatmax intensity. Unit of Measure: kilocalories per minute (kcal/min).

  3. Mean Exercise Heart Rate

    Time frame: 1 hour per experimental session

    Heart rate monitored continuously via a chest strap (Polar H9, Polar Electro, Findland) during the exercise test. Unit of Measure: beats per minute (bpm).

  4. Oxygen consumption

    Time frame: 1 hour per experimental session

    Volume of oxygen consumed during the exercise session measured breath-by-breath via indirect calorimetry using the Ergostik gas analyzer (Geratherm Respiratory GmbH, Germany). Unit of Measure: Liters per minute (L/min).

  5. Carbon Dioxide Production

    Time frame: 1 hour per experimental session

    Volume of carbon dioxide produced during the exercise session measured breath-by-breath via indirect calorimetry using the Ergostik gas analyzer (Geratherm Respiratory GmbH, Germany). Unit of Measure: Liters per minute (L/min).

  6. Blood lactate concentration

    Time frame: Every 20 minutes during each 1-hour session

    Measured from capillary blood samples taken from the fingertip during exercise to assess metabolic response to different caffeine interventions. Unit of measure: Millimoles per liter (mmol/L).

  7. Rating of Perceived Exertion (RPE) during exercise

    Time frame: Every 10 minutes during each 1-hour session

    Assessed using Borg's 6-20 scale; participants report perceived exertion at regular intervals. Unit of Measure: Units on a scale (from 6 to 20).

  8. Occurrence of caffeine-related side effects

    Time frame: Immediately after each session and 24 hours post-exercise

    Structured questionnaire assessing symptoms commonly associated with caffeine intake, such as nervousness, tremors, insomnia, gastrointestinal discomfort, and increased heart rate.

Sponsors and collaborators

Lead sponsor

Universidad Rey Juan Carlos

Other

Registry information

Official study title

Effects of Different Caffeine Ingestion Forms on Fat Oxidation During Cycle Ergometer Exercise

Important dates

Study start
2026
Primary completion
2026
Study completion
2026
First posted
Feb 11, 2026
Registry last updated
Apr 29, 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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