Caffeine Strategies and Fat Oxidation

Summary

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.

Conditions

• Fat Metabolism
• Caffeine
• Cycling
• Exercise
• Ergogenics

Interventions

OTHER

Placebo Mouth Rinse Solution

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

OTHER

Placebo (Cellulose Capsule)

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

OTHER

Placebo (Decaffeinated Coffee)

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

OTHER

Placebo (Non-caffeine Gum)

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

DRUG

Caffeine (Guinama Anhydrous Powder)

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

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.

DIETARY_SUPPLEMENT

Caffeine (Kafewake Gum)

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

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.

Sponsors & Collaborators

• Universidad Rey Juan Carlos

  lead OTHER

Principal Investigators

• Juan Del Coso, PhD · Universidad Rey Juan Carlos

• Arturo Casado, PhD · Universidad Rey Juan Carlos

Study Design

Allocation

RANDOMIZED

Purpose

BASIC_SCIENCE

Masking

DOUBLE

Model

CROSSOVER

Eligibility

Min Age

18 Years

Max Age

50 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2026-03-15

Primary Completion

2026-07-31

Completion

2026-09-30

Countries

• Spain

Study Locations