Caffeine, a compound present in foods such as coffee, tea, chocolate and energy drinks, is not only famous for its ability to activate us and keep us alert. It is also considered an ally in the field of physical performance, with a key role in energy metabolism and fat oxidation during exercise.
To understand the effect of caffeine we must first understand where and how the body gets energy. Briefly, muscle fiber cells extract energy from carbohydrates, fats and proteins. And they do it by converting everything into one of the “currencies” that cells understand: ATP or adenosine triphosphate. The energy density of the different “natural fuels” is different, with fats providing the most energy per gram of weight.
The body tends to maximum efficiency. And since humans are capable of storing more fat than carbohydrates, whenever possible our body will turn to fat for energy.
But there is a catch: since fats are large and complex molecules, breaking them down to obtain ATP is slower than with other substrates. Therefore, when we need a lot of energy in a short period of time, our body prioritizes the use of carbohydrates, which can be broken down more quickly to meet immediate energy demands.
Turning to carbohydrates has an important limitation. Its reserves in the body are limited, especially in the form of glycogen in the muscles and liver (we approximately have energy for about 60 minutes of intense work if we do not supplement during exercise). During prolonged or high-intensity exercise, such as a marathon or cycling, rapid depletion of reserves can lead to fatigue, decreased physical and mental performance, and sometimes soreness and muscle exhaustion.
Additionally, since the brain constantly requires glucose, low availability can affect concentration and the ability to make critical decisions during physical activity.
Beyond its known stimulating effect on the central nervous system, caffeine arouses particular interest due to its ability to positively influence fat oxidation during exercise. This implies that, under the effect of caffeine, our body tends to use more fatty acids as a source of energy in low and moderate intensities of physical exercise, thus reducing the oxidation rate of carbohydrates or muscle and liver glycogen.
This mechanism is particularly advantageous in sports disciplines such as cycling, marathons or triathlons, where preserving glycogen means that athletes can maintain a high level of performance for longer. It has also been discovered that caffeine helps preserve glycogen reserves in the muscles, postponing exhaustion and thus facilitating an improvement in performance.
After drinking a cup of coffee, this dark-colored concoction begins its journey through the stomach, then travels through the bloodstream to the brain, where it has effects that help us stay alert. But beyond keeping us awake, coffee has physiological effects related to the use of energy substrates during physical exercise.
The first effect is linked to adrenaline, that hormone that prepares us to run faster or jump higher in “fight or flight” situations. Under the effect of caffeine, adrenaline activates lipases (enzymes) that are responsible for breaking down stored fats (triglycerides), converting them into energy ready to be used in the muscles. By increasing the concentration of fatty acids in the blood, the use of fats as a source of energy increases.
At the same time, caffeine acts as a blocker of cellular adenosine receptors, allowing us to delay the feeling of fatigue. This way we manage to keep energy levels high and we can exercise for longer before feeling tired. As a consequence, we make better use of fats as a fuel source.
And does this increase in fat oxidation imply weight loss? Not necessarily. For weight loss to occur, there must be a negative energy deficit (calorie intake lower than calories expended). Furthermore, we are talking about a complex process that is affected by many variables, including hormones, psychological factors and lifestyle aspects.
Various studies confirm that caffeine increases fat oxidation in different populations, including both men and women. The effective dose usually starts at 3 mg/kg body weight, although the response may vary depending on the individual sensitivity of each person. This underscores the importance of customizing dosage to maximize metabolic benefits without compromising overall well-being.
Interestingly, recent studies indicate that caffeine intake improves fat oxidation in both the morning and afternoon, with as little as 3 mg/kg of body weight. But here's the surprising thing: It turns out that even believing we're drinking caffeine can boost this fat oxidation almost as much as actually drinking it. This teaches us something fascinating, not only about the power of caffeine but also about how our expectations can boost our athletic performance.
Everything indicates that caffeine is presented as a valuable tool for those seeking to optimize fat oxidation and improve sports performance. It acts not only as a powerful stimulant, but also as an effective promoter of the use of fats as a source of energy.
However, despite its benefits on sports performance, it is crucial to manage caffeine consumption carefully. Too much can trigger side effects such as nervousness, insomnia and an increase in blood pressure. The key to success lies in balance and personalization of consumption, always taking into account individual responses and needs, and adjusting the dose to find the perfect balance that improves performance without compromising health.
Plus, it's just extra help. The starting point should be to train well, eat healthy and on target, rest properly and be in a healthy mental state.
This article was originally published on The Conversation. Alejandro Muñoz is a Professor and Researcher in Physical Activity and Sports Sciences at the Francisco de Vitoria del Castillo University; David Varillas Delgado is a Professor of Physical Activity and Sports Sciences (CAFyD) and Coordinator of the Stable Research Group "Elite and High Performance Athletes" at the Francisco de Vitoria University; Jorge Gutiérrez Hellín is a Professor, Researcher and Communicator in the field of Health and Sports Performance; and Millán Aguilar Navarro is Professor of Physical Activity and Sports Sciences (CAFyD) and Coordinator of the Stable Research Group "Doping in Sports" at the Francisco de Vitoria University.
