Carbohydrate Periodization


Carbohydrate intake can be a source of confusion when it comes to nutrition and performance, and carbs can have a reputation of being bad for your body composition and performance. However, it is possible to find a healthy and effective way to make carbs work for you through carbohydrate periodization.

Carbohydrates are often associated with obesity and diabetes, since the overconsumption of calories through hyper-palatable carbs (simple sugars) can lead to weight gain and other associated health conditions. Some people even try to avoid carbs altogether (e.g., keto or fasting diets). Although this may result in short-term weight loss due to a reduction of calorie intake, it is not necessarily because all carbohydrates are terrible.

This post will give an overview into how carbohydrates function as an energy source for athletic performance, and how carbohydrate periodization can work to complement and enhance endurance training.

How do carbohydrates fuel athletic performance?

In performance terms, carbohydrates have traditionally been regarded as an inadequate fuel source, especially when compared to fats and proteins. This rationale is based on the facts that, gram per gram, fat contains more kilocalories than carbohydrate, and body fat stores are infinite compared to the limited stores of carbohydrate in the muscle, liver, and blood.

However, it takes longer for fat to convert into energy than it does carbohydrate. This means that, during high intensity activity the body burns carbohydrates primarily, since they break down quicker. When the carbohydrate stores are depleted the body needs to oxidise fat for energy, and performance intensity is reduced.

For this reason, in order to prepare the body for training, it is important to consider how much energy will be required, and allow for enough carbohydrate intake to make sure you are not overly relying on fat and protein stores. Your carbohydrate intake should reflect your training intensity, so a basic formula for your body’s fuel requirements would be: Energy required – fat and protein energy = carbohydrate energy requirement

What is carbohydrate periodization?

Simply put, carbohydrate periodization is the manipulation of your carbohydrate intake from day to day, or even meal to meal. Even more simply put, it’s a way to ration your carb intake to optimize how your body burns fuel during exercise.

Traditional nutritional plans tend to allow for the same level of carbohydrate intake every day, regardless of how your training schedule varies throughout the week. Depending on the training regime and goal, this might look like a consistently ‘high carb’ or ‘low carb’ diet. However, with carbohydrate periodization, the quantity of carbohydrate in your meals is adjusted to suit your training schedule, meaning that some meals will be high carb, and others will be low carb, depending on your needs.

Carbohydrate periodization takes a little more planning to get right, but it can have a significant impact on your performance.

How can carbohydrate periodization impact your performance?

If you are looking to optimize your high intensity and endurance fitness, there are various advantages to carbohydrate periodization, including:

  • Body composition 

For many athletes, it is very important to maintain an optimal power to weight ratio, so that your body is in shape for efficient practice without running a deficit on energy. If your carbohydrate intake is controlled to complement your training schedule (that is, varied depending on whether you are in a high intensity, low intensity, or rest stage), you can maintain your target weight without sacrificing performance.

  • Optimized performance

Carbohydrate periodization means that you make sure you have enough energy to fuel high intensity sessions, but reduce your intake during times of lower intensity, rest, and recovery periods.

  • Adaptations to exercise

In endurance training, the number of energy-producing cell mitochondria increases over time (this is known as mitochondrial biogenesis). This process may happen faster in low carb availability training. In addition, low carb training can also increase fat oxidation and improve overall fuel metabolism during exercise.

How can you incorporate carbohydrate periodization into your regime?

There are a number of ways to build carbohydrate periodization into your nutritional and training plan, so you can tailor your regime to fit your individual requirements:

  • Fasted Training 

This is when you go out to train first thing in the morning, before eating. You might find it convenient to get out of bed and train straight away, and some people feel good training on an empty stomach.

  • Split-session training 

This is when you train twice a day, usually in the morning and afternoon. Traditionally in this situation people have crammed carbs between sessions, but with carbohydrate periodization you would plan for the second session to be a low intensity or skill session, meaning that you can train in a low-carb state, and there is no need for aggressive refuelling.

  • Sleep low, train low 

This is when you restrict carbs after an evening training session. When you get up to train the next morning, you have even lower carbohydrate availability.

  • Recover low 

This involves restricting carbs following a session, and is usually combined with restrictions prior to and during training, for best effect.

A successful carbohydrate periodization regime should ideally combine a range of the above methods, incorporating high and low carbohydrate meal plans according to your training schedule and goals, so that you have the optimal energy stores for peak performance.

What are the risks of carbohydrate periodization?

There’s no such thing as a miracle fix. It’s very important to be aware of the physiological implications of any new nutritional plans, and make sure you take the time to find out what is right for you. While carbohydrate periodisation can be very effective in improving your ability to train, it can also have some drawbacks, including:

  • Lower energy availability

Carbohydrate periodization can actually sometimes have a detrimental effect on your exercise intensity. If you are working out at a high intensity on low stores of carbohydrate, you may struggle to keep up. Although low carbs may enhance adaptation, they may also deplete stores in big sessions. You need to be careful that you don’t get in too great a deficit. Even if you are trying to lose body fat, this isn’t an effective method. In fact it could well hamper your success overall.

  • Suppressed immune function

Carbohydrates are very important for supporting your immune system. If you have an insufficient store of carbs you may be more susceptible to infections, colds, and other illnesses, which can have a knock on effect on your performance. You could miss training sessions and competitions, which would negate any potential benefits.

  • Physiological issues

If done incorrectly, and over a prolonged period carbohydrate periodization can have a negative effect on bone health. It may result in a reduction in bone density, leading to stress fractures and even osteoporosis. This is another risk that may outweigh the advantages of a poorly thought-out nutritional plan.

Any new nutrition and training plan needs to be carefully considered in terms of the impact – positive and negative – it can have on your body. It’s important to be aware of the risks, so you make sure that you stay within healthy limits.


Carbohydrate periodization can be an effective method of making sure that you are accessing enough energy to perform according to the demands of your training schedule, and stimulate desired metabolic processes. However, if it’s worth doing, it’s worth doing properly, so it’s best to tailor your nutritional plan to fit your individual condition and requirements. If you do it right, you can avoid the pitfalls and access your optimal performance.