Caffeine Strategies and Fat Oxidation

Condition(s) studied

Investigational drug(s) / intervention(s)

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

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

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

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 (Cellulose Capsule): Opaque capsule containing cellulose powder, matching caffeine capsules, taken 60 min before exercise.

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

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

Placebo Mouth Rinse Solution: Decaffeinated Nescafé in 25 mL of water for a 20-second rinse immediately before exercise.

Study 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.

Eligibility

Primary outcome measure(s)

• Rate of fat oxidation during submaximal cycling exercise at Fatmax intensity — 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).

Trial sites (1)

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