Caffeine

Geschatte leestijd: 12 minuten Coffee is the world’s most commonly used psychoactive substance and thus has an effect on the psyche. In the case of coffee and the caffeine in coffee, it has a stimulating effect. On one hand by the action of the substance adenosine, which blocks drowsiness, but also by stimulating the central nervous system. However, coffee and caffeine have more properties that have made them one of the most popular supplements for athletes for decades.

Difference between coffee and caffeine

First and foremost, it is important to make a distinction between the effect of coffee and pure caffeine. After all, coffee contains more than just caffeine, which only forms two percent of coffee. Other substances in coffee can influence the effect of caffeine. Demonstrated effects of caffeine cannot always be extrapolated to the same amount of caffeine delivered in coffee or other beverages. Caffeine is a stimulant and can contribute to increased alertness, better concentration, and reduced fatigue. It stimulates the nervous system. Hence the association with coffee and staying awake. Formerly, caffeine was on the doping list for athletes as a stimulant, but that has not been the case since 2004. Since then, many elite athletes and recreational athletes have used caffeine as a supplement and performance-enhancing aid. Many studies show that caffeine can indeed improve performance through its positive effects on alertness, concentration, and fatigue. The caffeine in coffee takes effect after about 15 to 40 minutes, depending on age and weight. The effects can last up to 4 hours after ingestion. For recreational athletes, 1 cup of coffee before exercising can already improve alertness. After 1-3 cups, depending on the person’s weight, coffee can have a positive effect on endurance.

Caffeine as a pre-workout

Ask old school bodybuilders about the pre-workouts they used, and chances are most will mention caffeine among others. But even now, caffeine is still one of the few legal stimulants whose effect has been repeatedly demonstrated in independent studies.

Caffeine, endurance, and strength

As a performance-enhancing substance, coffee seems particularly suitable for endurance athletes given that its effect on endurance is greater than its effect on maximal strength. However, this does not mean it has no added value during strength training. Various studies have shown a positive effect, albeit limited and varying per muscle group. In addition, increased alertness can increase training intensity.

Caffeine and overall health

Many people try to avoid high caffeine intake. But what exactly constitutes a high intake and what adverse effects does this have? As a stimulant, a high daily dose of caffeine can lead to restlessness and insomnia, among other things. However, various studies have shown a link between coffee consumption and a higher life expectancy. So it is far too simplistic to see caffeine as a ‘guilty pleasure’. As described, caffeine offers several benefits. Therefore, it is important to have a good understanding of its effects on different areas and the corresponding dosage before deciding on its value in your individual case.

Caffeine and fat burning

The fact that caffeine has a particularly positive effect on endurance is partly due to its effect on fat burning. Caffeine promotes a higher burning of fatty acids as an energy source. However, fats provide longer and more gradual energy release, whereas carbohydrates mainly provide faster but shorter-duration energy. This also makes caffeine interesting for people who want to burn body fat. Thus, caffeine is one of the few legal and safe substances that demonstrably have a positive effect on fat burning. Caffeine and green tea (extract) are the only legal substances shown to actually have a fat-burning effect. For most fat burners, their effectiveness has not been or is insufficiently demonstrated in scientific research. Below, I will briefly discuss fat burners in general and then focus on caffeine in particular.

Caffeine as a fat burner

Earlier, I wrote an article about supplements; “Do I need supplements and if so, which ones?” Not an extensive article focusing on one supplement and supported by dozens of studies as usual on this site. Often people don’t want an extensive explanation of whether and why something works, but just the conclusion (and then apparently trust me on my beige biceps). The articles were therefore a brief overview of which supplements do and do not work based on the articles I previously wrote on this topic. In part of this article, I briefly discussed fat burners. I basically said “screw fat burners, losing weight is easy” due to the limited added value of fat burners (compared to exercise and a good diet). It won’t surprise you that this message is not one everyone likes to hear. So I received various questions about this: “But what about Dr. Oz’s raspberry ketones”, “And what about green tea”,”But surely, carnitine works?” That’s why in this additional part, I’ll go into more detail on this and describe various fat burners and the research that has been done on them.

What are fat burners?

But first, I’d like to delve into the concept of “fat burner”. Because what is a fat burner exactly? “Fat burner” is a collective term for dietary supplements claimed to have one or more of the following effects (1):

• Increased acute burning of fatty acids,
• General increase in energy expenditure,
• Increase in energy expenditure during meal digestion,
• Reduction in fat absorption,
• Promotion of weight loss,
• Increase in fatty acid oxidation during exercise,
• Long-term adaptations that increase fat metabolism.

Fat burners are often made from one or more ingredients claimed to exhibit one or more of the above properties. Additionally, there are products marketed as “fat burners” but primarily aimed at reducing appetite.

Mix of ingredients particularly commercially interesting

I’ve previously explained about creatine that there are constantly allegedly better or faster-acting variants being developed. Not necessarily because there’s a need for “better-working” versions of the already effective creatine monohydrate, but to differentiate themselves from other providers. Similarly, when creating a pre-workout, you can choose from the well-known ingredients everyone already uses, invent new ingredients and try to convince buyers that they work, or combine multiple known ingredients and claim that together they work even better. The same happens with fat burners. For example, green tea is not quite sold in the summer by your neighbor’s daughter next to her homemade lemonade, but almost everyone jumps on this hype. In the tea industry, good old earl grey has had to make way for earl green. Restaurants offer “green tea pesto” and even soy milk is sold with a green tea flavor. Others distinguish themselves by promoting new ingredients as fat burners to be the first to benefit when they are actually picked up by the general public. In such cases, it helps immensely if someone like Dr. Oz promotes this product, as was the case with raspberry ketones. Finally, there are manufacturers who combine multiple so-called fat-burning ingredients, claiming they are even more effective. A manufacturer buys various ingredients in bulk suspected of aiding fat burning. Then they combine them in a way that no one else has done before, and voilà! You have a new “fat burner”. In practice, this can mean that there is one ingredient that can truly have an effect, but it’s now in too small a dosage in favor of 10 other ingredients that sound nice but do nothing. The fact that there’s often no scientific basis for such a new fat burner seems not to matter; Neither for the manufacturer nor for the consumer. In that respect, most of us are happy to believe anything. It’s much easier to believe in a miracle pill than to accept that you need to eat less and/or healthier and exercise more.

University of Birmingham Research on Fat Burners

In a study by the University of Birmingham, not all fat burners or ingredients thereof were studied. This is simply not possible given the speed at which this market is growing. The number of new fat burners far outpaces the research aiming to demonstrate their effectiveness. The Birmingham study focused on substances for which there is sufficient research to draw a well-founded conclusion. They looked at as many studies involving humans as possible. If these were not available, they also considered animal studies. In total, they found 82 relevant studies. The “fat burners” they evaluated are:

• Caffeine
• Carnitine
• Chromium
• Fucoxanthin (ingredient of wakame, a type of seaweed)
• Green tea extract
• Kelp (“bladderwrack”, a type of seaweed)
• Taurine
• CLA
• Forskolin
• (Regular) Tea

Of all these so-called fat burners, only caffeine and green tea have been shown to have a significant effect on fat burning (in various ways). For the rest, the evidence is lacking.

Based on the available literature, caffeine and green tea have data to back up its fat metabolism-enhancing properties. For many other supplements, although some show some promise, evidence is lacking. The list of supplements is industry-driven and is likely to grow at a rate that is not matched by a similar increase in scientific underpinning. A.E. Jeukendrup, University of Birmingham

This research is useful for an overview of the various relevant studies, but for a thorough understanding, you need to dive into the studies they mention yourself. Unfortunately, the researchers themselves seem to have some shortcomings. For example, in references to other studies, they do not mention when these were conducted on behalf of companies selling the products being studied. Something that should always be mentioned in my humble opinion. In another case, for example, they refer to a study that is supposed to demonstrate the effects of caffeine while in this study it was combined with ephedrine. Therefore, I will delve deeper into some studies they mention and/or compare them with other relevant studies they do not mention.

Caffeine as a fat burner

Various properties of caffeine have been discovered that can result in less body fat:

• Increased oxidation (burning) of fats during activity (2)
• Shift in the ratio between carbohydrate and fat burning more towards fats (3)
• Increased activity of the (ortho)sympathetic nervous system (the part of the nervous system that puts the body in a state of readiness/action) (1)
• Increased resting metabolism (5-7)

“Caffeine increases resting metabolism”

You can classify the way your body uses energy into three types of metabolism (harada).

• Resting metabolism
• Expenditure for activity
• Expenditure for meal processing

60-75% comes from resting metabolism, the energy your body uses for all (semi-)autonomous processes such as heart rate, brain function, and respiration. 20% of energy is consumed by daily activity. Finally, processing food accounts for about 10% of our total energy expenditure. Researchers observed in 1989 that intake of 100mg of caffeine resulted in a 3-4% higher resting metabolism in the 150 minutes following ingestion (6). This increased to 8-11% when this intake was repeated every two hours for 12 hours (thus 6 intakes). However, it is not certain that this increased burning is due to increased fat or carbohydrate burning (7). Researchers in Switzerland conducted four different trials (5). They looked at the effect of different intakes of caffeine on the metabolism of different individuals during the three hours after ingestion. They first compared the effect of daily intake of a caffeine capsule, a total of 8mg per kilogram of body weight, on ordinary, healthy people with that of a placebo on a control group. The amount of calories burned at rest in the caffeine group increased by 20% from one and a half hours to the end of the three hours. Over the three hours, it was an average increase of 16%. In the control group that received a placebo, this (not statistically significant) decreased by 3%. However, the results in the caffeine group varied considerably, between 8 and 30 percent. This may be due to the amount of coffee the subjects usually drink (see further). Unfortunately, the study does not mention anything about this. From the fact that more free fatty acids were measured in the blood in the caffeine group (especially in the third hour after ingestion), it can be inferred that more fats are burned. Carbohydrate consumption remained the same. In the second trial, less caffeine was ingested (4mg per kilogram of body weight) and in regular coffee form, compared to caffeine-free coffee and a placebo. This way, you can assess whether the effects are caused by the caffeine in the coffee. In both “coffee groups,” metabolism increased in the three hours after ingestion, but more in the caffeine group. Here, it increased by an average of 12%, while caffeine-free coffee resulted in an increase of 5%. Unfortunately, the results of the placebo group are not shown here. Again, fat burning increased, this time accompanied by a decrease in carbohydrate use. So, burning more fats and less sugars. The lower increase in the caffeine group compared to the first trial is very likely due to the halved dosage. The 5% increase in the caffeine group compared to the 3% decrease in the placebo group in the first trial is striking. Is this due to other substances in coffee that (also) contribute to an increased metabolism, is it due to the small number of people in the study, or does the background of the participants also play a role here?

“Caffeine less fat-burning in overweight people”

In the third trial, the same amount of coffee was again compared to caffeine-free coffee and a placebo. This time, the effect on obese people was compared to “normal” people. In contrast to the previous trials, there was no difference between regular coffee, caffeine-free coffee, and the placebo group. Nor did the number of free fatty acids in the bloodstream increase now. This corresponds to other studies showing that overweight people are “less sensitive to fat-burning stimulants” (1). There is a Danish study that shows good results in overweight women, but in that study, caffeine is mixed with ephedrine (known from the now banned “stackers”) (9).

“Caffeine increases metabolism after a meal”

In the fourth and final trial, the effect of coffee was again compared to caffeine-free coffee and a placebo. This time, however, on metabolism after eating a breakfast of about 736 kcal. This increased in both groups (logical after eating a meal), but more in the caffeine group than in the caffeine-free group. Fat burning also increased only in the caffeine group.  Caveats of the research This research from Switzerland was done in collaboration with Nestlé. This does not automatically mean that the research was not well conducted or that the data is not well represented, but it is not truly objective. Also, the numbers of subjects per trial are not particularly large, namely only 6 to 7 individuals. Perhaps even more important is that we do not know how much coffee they drink in their daily lives. People who consume a lot of caffeine (> 300mg/day) may become less sensitive to it and therefore experience less of its effects (10,11). This was evident, for example, when a fat burner containing both green tea and caffeine had no effect on people who regularly drink coffee but did on others.

Side effects and disadvantages of Caffeine

There will be plenty of people who don’t like to hear caffeine mentioned as a fat burner. They have made the effort to switch to caffeine-free coffee. Caffeine is associated with high blood pressure and anxiety (12). Additionally, it has a negative effect on cholesterol, which can cause cardiovascular diseases (13). Researchers at the University of Copenhagen who gave their participants 100mg, 200mg, or 400mg of caffeine per day found that there were hardly any side effects reported at 100mg and 200mg (8). However, at 400mg, there were several reports of palpitations (4 out of 6 participants), three of the six participants reported feelings of anxiety, three had headaches, two felt restless, and one participant experienced dizziness. However, there are many people who function fine at 600mg or more per day (12). That does not mean that their bodies do not experience adverse effects from caffeine, but in those cases, they may not yet be noticed. An important point for muscle builders is that caffeine affects the adenosine receptors involved in muscle energy supply. This means that “quitting coffee” in heavy coffee drinkers leads to muscle fatigue (14).

Caffeine: General health benefits and recommended amount

However, caffeine also has benefits for overall health. There have been studies that showed a negative association with diabetes, certain types of cancer, Parkinson’s, and Alzheimer’s (13). Caffeine could therefore reduce the risk of these conditions. Additionally, it improves cognitive brain functions (13). To make a long story short: There is still debate about whether the benefits of coffee outweigh the drawbacks. Considering that 2-3 cups of coffee per day would provide many of the benefits while the drawbacks often occur with excessive use, this amount is recommended (13). However, this depends on the strength of the coffee, which can vary between 50mg and 150mg per cup. With 3 cups of strong coffee containing 150mg per day, you are both above the threshold at which the Danish study found many side effects and above 300mg per day, where the fat-burning effects no longer seem to occur.

Conclusion and summary

For most fat burners, the effectiveness cannot be demonstrated or is barely proven in research. Caffeine is one of the few exceptions whose fat-burning properties have been demonstrated in various studies. Caffeine appears to increase metabolism both at rest, during activity, and after eating a meal. This increase seems to be mainly caused by an increase in burned fatty acids. Some studies did not show the added value. Especially people with obesity and those who consume more than 300mg of caffeine per day seem to have less or no benefit from it. To be clear: If you are overweight, coffee or caffeine, and most likely any other “fat burner,” is not the solution. Ultimately, I still say that the differences in burning that caffeine can cause are very small compared to the results you can achieve from diet and exercise. I think the differences become truly significant in subjective terms (so that you really feel personally that you have improved) when you are already relatively lean and with coffee can become just that little bit drier. Especially when you are already dry training with the help of a reduced diet. To benefit from the advantages of caffeine while limiting the chances of the disadvantages, drink a maximum of 2-3 cups of coffee per day, depending on the strength. References

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