There has been a big discussion in the last two decades about which diet supports the best athletic performance. Some proponents are in favor of high-carbohydrate diets, while others defend that a low-carbohydrate diet works better.
In that discussion, a new approach emerged: periodized nutrition. Instead of promoting one diet over the other, it advocates for changing your macro- and micronutrient intake depending on the training cycle (micro-, meso- and macrocycle). Jeukendrup gave this definition for that approach: "the planned, purposeful, and strategic use of specific nutritional interventions to enhance the adaptations targeted by individual exercise sessions or periodic training plans, or to obtain other effects that will enhance performance in the longer term". In other words, changing what we eat to get different (positive) outcomes out of our training.
This approach is key to individualize the training for a given athlete, as we don't want the same adaptations for each athlete. His history, goals, lifestyle, level, stress and many other factors have to be taken into consideration and plan nutrition accordingly.
When thinking about training adaptations, some approaches have shown to increase them.
Training in a low-carbohydrate availability state can increase the expression of PGC1α, which is the master regulator for mitochondrial biogenesis (the energy producers of our cells). This can be achieved in different ways: not ingesting any carbohydrate during a demanding and long ride; depleting the glycogen stores in an afternoon workout, not having carbohydrates after that and training fasted the followed morning; training fasted...
Opposite to that, one practice is training in a high-carbohydrate availability state. Loading the glycogen stores and having exogenous (ingested while exercising) carbohydrates achieves that, and it is used to promote high-intensity training and its adaptations, as well as training the gut to tolerate high amounts of carbohydrate (for race day), practicing race-day nutrition...
A simple tweak in energy availability will also change adaptations: if we consume considerably fewer calories than burned in an energy-demanding day the adaptations will also be enhanced.
Tweaking other macronutrients also play an important role. When a high load is present, an increase of protein supports the adaptations. Also, when aiming to lose weight an increase in protein is suggested to maintain muscle mass, force production and performance (instead of the normal 1.2-1.5g/kg/day, consuming up to 2g/kg/day of protein).
If the target event will be in a hot environment and dehydration is a possibility, training dehydrated is a good strategy to adapt and suffer fewer bad consequences when getting dehydrated next time.
In the case of cyclists, we can divide them into different groups: sprint and anaerobic athletes (from 5s to 3min), short endurance athletes (from 3min to 2h) and long endurance athletes (over 2h). All of these have different energy demands and need different adaptations.
In the case of sprint and anaerobic athletes, they need a big amount of fast-twitch fibers, good tolerance for acidosis, high peak production of force, and good utilization of lactate. For these, a train-low approach is not very wise, as they need glycogen to fuel and they don't need the aerobic adaptations that are achieved with that approach. For them following a constantly high-carbohydrate diet makes more sense.
With the punchy rider, carbohydrates are still the only fuel source but they can benefit from a train-low approach to increase mitochondrial adaptations, as that could improve their performance.
For the long endurance athlete, the train-low approach is a serious consideration. In those durations glycogen stores are not sufficient to endure, and there is a need to use fat as a source of energy. By implementing training low strategies the fat utilization can be further increased and could give some benefits for that kind of performance.
However, nutritional periodization is not the best approach always. Burke compared a high-fat diet, a periodized diet and a high-carb diet with race walkers in the Supernova project. While the high-fat diet increased fat utilization, their performance was worse. The periodized approach also was inferior to the high carbohydrate diet. That is because fat is less economical than carbohydrates (around 5-6%): it creates less energy for the same amount of oxygen. When you need to produce energy as fast as possible, without the limitation of emptying glycogen stores, a greater performance is achieved using carbohydrates.
Another example of this is the Breaking 2 project. When Kipchoge tried to break the 2h mark in the marathon, he used a high-carbohydrate diet all the time so he uses only carbohydrates when running at the target pace. That way, he will be the most economical that he can be and achieve his best possible performance. So, for time trialists, hill climbers, short-distance triathletes... following a high-carbohydrate approach will yield a greater performance.
But, for other athletes, that can differ. In cycling we often have mixed terrain and mixed efforts: we have a 6 hours long race but the decisive part is a short climb and the final sprint. In that case, good utilization of fat is essential to get to the end with glycogen stores available but good use of carbohydrates is needed to do those short efforts. In those cases, periodizing nutrition is a good approach as we can improve both aspects (maybe not to their greater potential).
As seen, periodizing nutrition is not the magic key. It is another approach to individualize more the training process, but it is just a tool that needs good hands to be used properly. Taking into account the athlete, his targets and his circumstances we can decide if that approach is useful, if it will benefit the athlete and how to use it.
- Burke, L. (2006). Clinical Sports Nutrition. 3rd edition. Sydney: McGraw-Hill
- Burke, L. (2017). "Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers". The Journal of Physiology, 595(9), pp. 2785-2807.
- Jeukendrup, A. (2017). "Periodized Nutrition for Athletes". Sports Medicine, 47(1), pp. 51-63.
- Jeukendrup, A. (2019). Sport Nutrition. 3rd edition. Champaign, IL: Human Kinetics.
- Stellingwerff, T. (2019). "A Framework for Periodized Nutrition for Athletics". International Journal of Sport Nutrition and Exercise Metabolism, 29(2), pp. 141-151.
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