Caffeine Strategies and Fat Oxidation

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

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.

Study Overview

• Status: Enrolling by invitation
• Conditions: Exercise; Caffeine; Ergogenics; Cycling; Fat Metabolism
• Intervention / Treatment: Drug: Caffeine (Guinama Anhydrous Powder); Other: Placebo (Cellulose Capsule); Dietary supplement: Caffeine (Nescafé Classic Coffee); Other: Placebo (Decaffeinated Coffee); Dietary supplement: Caffeine (Kafewake Gum); Other: Placebo (Non-caffeine Gum); Other: Caffeine Mouth Rinse Solution; Other: Placebo Mouth Rinse Solution

• Study Type: Interventional
• Enrollment (Estimated): 10
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Spain
  • Madrid
    • Fuenlabrada, Madrid, Spain, 28942
      • Estadio Raúl González Blanco, Camino del Molino 5

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

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

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Double

Number of Arms

8

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Caffeine capsule; Participants will ingest 3 mg/kg of anhydrous caffeine powder in an opaque capsule 60 minutes before performing 60 minutes of cycling on a cycle ergometer at Fatmax intensity.	Drug: Caffeine (Guinama Anhydrous Powder); 3 mg/kg of anhydrous caffeine powder (Guinama, Spain) administered in an opaque capsule 60 min before exercise.
Placebo Comparator: Placebo capsule; Participants will ingest an opaque capsule filled with cellulose (placebo) 60 minutes before performing 60 minutes of cycling on a cycle ergometer at Fatmax intensity.	Other: Placebo (Cellulose Capsule); Opaque capsule containing cellulose powder, matching caffeine capsules, taken 60 min before exercise.
Experimental: Caffeine coffee; Participants will consume 3 mg/kg of caffeine via soluble coffee (Nescafé Classic) in 250 mL of hot water 60 minutes before performing 60 minutes of cycling on a cycle ergometer at Fatmax intensity.	Dietary supplement: Caffeine (Nescafé Classic Coffee); 3 mg/kg of caffeine via Nescafé Classic (Nestlé, Switzerland) dissolved in 250 mL of water 60 min before exercise.
Placebo Comparator: Placebo coffee; Participants will consume decaffeinated soluble coffee (Nescafé Descafeinado) in 250 mL of hot water 60 minutes before performing 60 minutes of cycling on a cycle ergometer at Fatmax intensity.	Other: Placebo (Decaffeinated Coffee); Decaffeinated Nescafé (Nestlé, Switzerland) in 250 mL of water, matching caffeinated coffee, taken 60 min before.
Experimental: Caffeine chewing gum; Participants will chew caffeinated gum (Kafewake) containing 3 mg/kg of caffeine for 10 minutes before performing 60 minutes of cycling on a cycle ergometer at Fatmax intensity.	Dietary supplement: Caffeine (Kafewake Gum); 3 mg/kg of caffeine via Kafewake gum (Arafarma group, Spain), chewed for 10 min before exercise.
Placebo Comparator: Placebo chewing gum; Participants will chew non-caffeinated gum (Kafewake) with identical flavor and texture for 10 minutes before performing 60 minutes of cycling on a cycle ergometer at Fatmax intensity.	Other: Placebo (Non-caffeine Gum); Kafewake Non-caffeinated gum (Arafarma group, Spain) with identical taste and texture, chewed for 10 min before.
Experimental: Caffeine mouth rinse; Participants will perform a 20-second mouth rinse with 25 mL of water containing 3 mg/kg of caffeine from soluble coffee (Nescafé Classic) before performing 60 minutes of cycling on a cycle ergometer at Fatmax intensity.	Other: Caffeine Mouth Rinse Solution; 3 mg/kg of caffeine (Nescafé Classic) dissolved in 25 mL of water for a 20-second rinse before exercise.
Placebo Comparator: Placebo mouth rinse; Participants will perform a 20-second mouth rinse with 25 mL of water containing decaffeinated soluble coffee (Nescafé descafeinado) before performing 60 minutes of cycling on a cycle ergometer at Fatmax intensity.	Other: Placebo Mouth Rinse Solution; Decaffeinated Nescafé in 25 mL of water for a 20-second rinse immediately before exercise.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Rate of fat oxidation during submaximal cycling exercise at Fatmax intensity	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).	1 hour per experimental session

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Rate of carbohydrate oxidation during submaximal cycling exercise at Fatmax intensity	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).	1 hour per experimental session
Total energy expenditure during exercise	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).	1 hour per experimental session
Mean Exercise Heart Rate	Heart rate monitored continuously via a chest strap (Polar H9, Polar Electro, Findland) during the exercise test. Unit of Measure: beats per minute (bpm).	1 hour per experimental session
Oxygen consumption	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).	1 hour per experimental session
Carbon Dioxide Production	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).	1 hour per experimental session
Blood lactate concentration	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).	Every 20 minutes during each 1-hour session
Rating of Perceived Exertion (RPE) during exercise	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).	Every 10 minutes during each 1-hour session
Occurrence of caffeine-related side effects	Structured questionnaire assessing symptoms commonly associated with caffeine intake, such as nervousness, tremors, insomnia, gastrointestinal discomfort, and increased heart rate.	Immediately after each session and 24 hours post-exercise

Collaborators and Investigators

• Sponsor: Universidad Rey Juan Carlos
• Investigators: Principal Investigator: Juan Del Coso, PhD, Universidad Rey Juan Carlos; Principal Investigator: Arturo Casado, PhD, Universidad Rey Juan Carlos

Publications and helpful links

General Publications

• Guest NS, VanDusseldorp TA, Nelson MT, Grgic J, Schoenfeld BJ, Jenkins NDM, Arent SM, Antonio J, Stout JR, Trexler ET, Smith-Ryan AE, Goldstein ER, Kalman DS, Campbell BI. International society of sports nutrition position stand: caffeine and exercise performance. J Int Soc Sports Nutr. 2021 Jan 2;18(1):1. doi: 10.1186/s12970-020-00383-4.
• Ruiz-Moreno C, Gutierrez-Hellin J, Amaro-Gahete FJ, Gonzalez-Garcia J, Giraldez-Costas V, Perez-Garcia V, Del Coso J. Caffeine increases whole-body fat oxidation during 1 h of cycling at Fatmax. Eur J Nutr. 2021 Jun;60(4):2077-2085. doi: 10.1007/s00394-020-02393-z. Epub 2020 Oct 6.

Study record dates

Study Major Dates

• Study Start (Actual): March 15, 2026
• Primary Completion (Estimated): July 31, 2026
• Study Completion (Estimated): September 30, 2026

Study Registration Dates

• First Submitted: January 13, 2026
• First Submitted That Met QC Criteria: February 3, 2026
• First Posted (Actual): February 11, 2026

Study Record Updates

• Last Update Posted (Actual): April 29, 2026
• Last Update Submitted That Met QC Criteria: April 28, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Behavior; Motor Activity; Heterocyclic Compounds; Heterocyclic Compounds, 2-Ring; Heterocyclic Compounds, Fused-Ring; Carbohydrates; Alkaloids; Purinones; Purines; Polymers; Macromolecular Substances; Biomedical and Dental Materials; Manufactured Materials; Technology, Industry, and Agriculture; Polysaccharides; Glucans; Biopolymers; Xanthines; Caffeine; Cellulose
• Other Study ID Numbers: URJC-CAF-FOX-2026

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: De-identified individual participant data underlying the results reported in publications may be made available upon reasonable request. These data may include anonymized metabolic, ventilatory, cardiovascular and perceptual variables collected during the study (e.g., fat oxidation rate, energy expenditure, VO₂, VCO₂, heart rate, capillary blood lactate concentration, and ratings of perceived exertion). Any data sharing will be subject to ethical approval, compliance with applicable data protection regulations, and approval by the study investigators.
• IPD Sharing Time Frame: De-identified individual participant data may be shared after the publication of the main study findings and will remain available for up to three years following publication.
• IPD Sharing Access Criteria: Access to any de-identified individual participant data will be considered on a case-by-case basis. Requests will require a scientifically sound proposal and may be subject to additional ethical review and data use agreements, in accordance with institutional and legal requirements. The study investigators reserve the right to decline requests.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ICF

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No