Low Carb Training: Train more effectively without carbohydrates


Those who forgot carbohydrates before and during training cannot only improve their fat metabolism and aerobic endurance, but also shorten their training time if cleverly timed. 

Low carb, low sugar, or even training on an empty stomach have become more and more relevant in cycling in recent years. While it was the professionals who first started looking into and using this training method, meanwhile more and more non-professional athletes of all performance levels have come to tackle it, too, i.e., they train their body to use mainly fatty acids as fuel and carbohydrates only during more intensive sessions.  

“Train low” is a generic term for all forms of this periodized nutrition, which all have in common that athletes already start into their training sessions with a reduced carbohydrate availability. But why is this kind of training necessary at all? 

The aim of this kind of training for amateur athletes is, for example with regard to a cycling marathon, to reduce the metabolization of carbohydrates and to train the fat metabolism. This form of training economizes and enlarges the mitochondria – i.e. the power plants in the muscles – which also improves the maximum oxygen intake. 

Low carb training: using fats as fuel  

“While fats are available in abundance and can be regarded mathematically as an almost “infinite” quantity, carbohydrates are nevertheless always the dependent variable when choosing a substrate”, explains professional coach Björn Geesmann from HYCYS (www.hycys.de). If carbs are available, the body will use them for fuelling in larger quantities and hardly use fats. 

If there is a permanent supply of carbohydrates, this leads to a permanently high carbohydrate consumption and generally poor fat metabolism. If carbohydrates are only available in a reduced form, the body has to adapt and use more fats. 

The energy production of our organism is comparable to a hybrid engine in a car. The human “engine” uses fats and carbohydrates as fuel up to the individual anaerobic threshold. 

As soon as the threshold is reached, it runs on carbohydrates only. Unlike in a car, human athletes do not have a switch to select the fuel source but must train their hybrid engine to produce energy efficiently, i.e., to use fat. If they manage to do so, they do not have to re-load on fuel quite as often, because fats are an “infinite” energy source, carbohydrates are not. 

Low carb training provides a strong training stimulus 

If the organism is provided with few carbohydrates, energy supply processes will change, and the body will furthermore be stressed in addition to the regular training stimulus. “On the plus side there are important physiological and hormonal adjustments with effects such as reduced carbohydrate consumption and, as a result, an optimized fat metabolism,” explains sports scientist Björn Geesmann. 

“On the debit side, there is an increased susceptibility to infection and greater fatigue,” says Geesmann. In addition, muscles may suffer when the organism tries to convert muscle protein into glucose, i.e. fuel, in the absence of carbohydrates. 

This risk can be significantly minimized by a protein- or fat-rich diet – before, after or even during training,” says Björn Geesmann. After all, it is not about reducing the amount of calories taken in, but about periodizing the carbohydrate intake only. The effects of an improved fat metabolism can be generated simply by using carbohydrates differently, i.e. by cleverly timing their intake. 

Training on an empty stomach: for ambitious athletes only  

If you want to forgo carbohydrates, why not train on an empty stomach? “Some pros do this as well”, explains Geesmann, but considers this approach a bit too risky for non-professional cyclists. “In this case glycogen stores run usually very low and the organism may react with blood sugar fluctuations due to the lack of nutrients, which runs counter to the goal,” says the sports scientist. 

Low carb training has proponents and opponents. It is undisputed that the training stimulus and the influence of these epigenetics are great. But anyone who wants to train this way must be aware of the special circumstances. It may well be the case that the performance of some athletes decreases. “You often hear from within the professional peloton that this kind of training is of no use for sprinters,” says Geesmann. 

“But I know of coaches who use it successfully for sprinters to keep them fresh for the last 1000 metres. In this case, too, it is a question of timing, dosage and, of course, the physiology of the athlete,” says the sports scientist. 

Tips for riding with reduced carbohydrate stores 

If you have never completed a low carb training session, it is not recommended to start with the most extreme option right away, i.e. to deliberately empty the stores with a training ride in the evening and complete the next session after a low carb breakfast the morning after.  

The better option is to climb on the bike, maybe even on the bike turbo, rested and after a low-carbohydrate breakfast, to complete an hour-long easy ride and see what happens. The scope – but not the intensity – can then be increased from time to time. Stay roughly in the lower GA1 range intensity-wise. 

If you like to play by numbers: modern performance diagnostics, including ergospirometry, do not only determine the maximum lactate formation rate, but also the optimal training intensity for a so-called FATmax training. “This is the zone in which the athlete actually metabolises most fat,” says Geesmann. 

Low carb training: stress for the immune system

As this form of training is extremely stressful for the body due to the shortage of carbohydrates and stimulates the immune system a lot, athletes must be rested and not the least be fatigued. “Furthermore, athletes should consume carbohydrates afterwards and maybe not join large crowds immediately,” Geesmann advises. 

Forgoing carbohydrates after training is also a way of prolonging or increasing the stimulus set by the training. “I would advise against this, however, as stress always has a two-way effect, i.e., improved adaptation versus a worsened general condition,” says the sports scientist. Moreover, the data situation is still too vague on this.