Why carbs are king

Carbohydrates are the most studied nutrient in sports. No other nutrient has been studied as much and from as many aspects as carbohydrates. And yet there are still many questions about the role and requirements of carbohydrates. The opinions of the population are sometimes very different about this. Experts have been in agreement on sports nutrition since the 1960s. If you train a lot and hard, you need lots of carbohydrates. Back then, in the first, very simple experiments, it was observed how the performance differs between people who consume a lot or a little carbohydrates. If you eat a few carbohydrates, you get tired more quickly and cannot carry out intensive exercise for as long as someone who consumes more carbohydrates. Over the years, researchers have also recognized how carbohydrate intake during exercise affects athletic performance. For example, we now know that the intake of carbohydrates is important with increasing exercise duration and, especially during intensive, recurring efforts, the intake of carbohydrates has positive effects on performance.

Since 1990, we have known how glycogen stores affect performance

In the 1990s, in very advanced sports science studies at that time, Coyle and his colleagues investigated the impact of physical activity on our carbohydrate stores (glycogen) and what happens as glycogen levels decrease. Today's sports nutrition continues to build on these findings, even though we now know much more. Knowledge about carbohydrates has improved significantly over the years. On the one hand, there is health... On the one hand, we see in many cases what too many simple and nutrient-poor carbohydrates are doing to our body (including chronic diseases), and on the other hand, we also have a great deal of valuable data on nutrient-rich, health-promoting carbohydrates from primarily complex, nutrient-rich varieties. In addition to health, there is also sport, where carbohydrates play an important role. They are the main energy substrate for human muscles when exposed to moderate to intensive loads. In addition, our brain also loves carbohydrates and consumes around 120 g of carbohydrates a day. This means that on rest days or easy days the brain consumes the majority of the carbohydrates we consume. In fact, the recommendations for daily carbohydrate intake on rest days take into account exactly this requirement (3-4 g/kg/d).

However, sport is not just about the brain, but above all about the energy supply for the muscles. The demand can be very high on intensive training days and bars, gels and drinks help us to meet the demand. They are usually concentrated sources of carbohydrates and make it easier for athletes to reach large amounts during exercise. Large quantities, i.e. 60 to 90 g/h - ranges that many athletes often do not reach, according to scientific research. For some, lower amounts such as 30-40 g/h already seem “a lot”, but in reality these are not large amounts and often too few carbohydrates. The number 30 seems huge, but is actually very low when it comes to the amount of carbohydrates. It is definitely not enough if you want to provide intensive exercise with energy. And it is too little when you consider how many carbohydrates the human body uses during intensive exercise.

Low carb follows high carb

The current recommendations for longer, more intensive workouts are up to 90 g carbohydrates per hour. These quantities are based on studies on the absorption rate of different carbohydrates. In some cases, even around 120 g/h is useful; according to recent studies, our body can still absorb this amount. However, since the focus in the 1990s and early 2000s seemed mostly on carbohydrates due to findings from carbohydrate research, people got the impression that nutrition experts always recommended large amounts. So then there was a new trend to reduce carbohydrates and low carb in sport. Suddenly, many athletes have started to reduce carbohydrates, sometimes completely avoid them. The low-carbohydrate diet was also often associated with the desire for a lower body weight. In the last 15 years, however, the desire to improve fat oxidation has also become more and more important. For example, there are now many who constantly want to train fat oxidation and constantly go through training weeks with low carbohydrate intake.

In the first phase of this dietary change, there is usually a significant weight loss. It is simply explained and has nothing to do with fat loss. Some people lose 3-5 kg in the first week. A lot of glycogen, which is no longer replenished due to the low carbohydrate intake, and a lot of water, which is otherwise stored with the glycogen. Yet weight loss motivates and some go one step further, reducing carbohydrates even more. However, the assumption that carbohydrates make you fat, the far too central, permanent goal of improved fat burning and the associated undersupply of the body leaves its mark.

The body can only handle this for a certain period of time, then it starts to struggle. These 30 g/h of carbohydrates in one unit are usually still too high for those who are low carb and go even lower. But 30 g/h is virtually nothing... then comes low intake during the day…this low carbohydrate intake is often associated with a significant energy deficit. Recent surveys show that this inadequate carbohydrate intake impairs performance and can also cause massive damage to the body. For example, bone health is impaired and in some cases athletes have poor bone density levels that diagnose someone with osteopenia or osteoporosis. Underfuelling of several months can lead to osteoporosis. But low carbohydrate intake and associated low carbohydrate availability and often low energy availability (REDs!) , can cause far more. Among other things, poor insulin metabolism, impaired blood sugar management, decrease of performance, amenorrhea. When people have REDs, we now know many symptoms that are triggered by insufficient intake. The IOC Consensus Statement on Relative Energy Deficiency in Sport (2023) also points out the role of carbohydrate availability. The problem that it is often too low also contributes to the many cases of REDs.

Fuel to achieve the dream

The trend towards an excessive low-carbohydrate diet in sport has contributed to many problems that we are increasingly observing in recent years. That is why it is important in sport that we move away from the idea of chronically reduced carbohydrate intake. No one has to eat excessive amounts of carbohydrates if the level of physical activity is low. But it is important that carbohydrate intake increases as training volume and intensity increase. Low carb and peak performance (including intensive, long training days) only work for a very short time, then the problems start, and they may last a lifetime. The current carbohydrate intake recommendations take into account different exercise intensities and duration of the sessions. Anyone who implements these principles correctly doesn't need be afraid of unwanted weight gain. These basics help you achieve top performance and achieve your own dreams.

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Further reading:

Coyle et al (1991) Timing and Method of Increased Carbohydrate Intake to Cope with Heavy Training, Competition and Recovery. Journal of Sports Sciences, 9:S1, 29-52, DOI: 10.1080/02640419108729865.

Jeukendrup (2014). A Step Towards Personalized Sports Nutrition: Carbohydrate Intake During Exercise. Sports Med, 44 (Suppl 1) :S25—S33. DOI 10.1007/s40279-014-0148-z.

Mountjoy et al (2023). 2023 International Olympic Committee's (IOC) consensus statement on Relative Energy Deficiency in Sport (REDs). Br J Sports Med, Sep 57 (17): 1073-1097. doi: 10.1136/bjsports-2023-106994.

Sale et al. (2015) Effect of carbohydrate feeding on the bone metabolic response to running. J Appl Physiol 119:824-830. doi:10.1152/japplphysiol.00241.2015.