Training with restricted carbohydrate availability (RCA), also known as low carbohydrate or carbohydrate restriction, is a dietary approach that involves reducing the intake of carbohydrates.
This training might manifest in the form of early-morning sessions before breakfast, in a fasted state or twice-daily sessions, with minimal refuelling within or in-between workouts.
I have already trained in a fasted state over 30 years ago, so it is not a ground breaking training method!
Training with RCA can be done for various reasons, including weight loss, improved blood sugar control in people with diabetes, and performance enhancement in athletes.
There is some evidence to suggest that training with carbohydrate restriction can lead to a number of physiological adaptations that may improve physical performance.
Impact of RCA training on fat oxidation
Training with restricted carbohydrate availability can have a number of effects on the body’s ability to burn fat for fuel, also known as fat oxidation.
One of the main effects of carbohydrate restriction is to increase the production of certain hormones. For example, glucagon and human growth hormone (HGH) play a role in stimulating the breakdown of fats in the body.
Additionally, when carbohydrate intake is limited, the body is forced to rely more on fat as a fuel source, which can lead to an increase in fat oxidation.
There is some evidence to suggest that training with carbohydrate restriction may lead to an increase in fat oxidation during exercise, particularly during endurance exercise.
This can be beneficial for athletes looking to improve their endurance and performance, for instance enhanced FU (fractional utilisation of V02max) and increased threshold power/speed, as well as for individuals seeking to lose weight (non-functional body-fat).
It is important to note, however, that the effects of carbohydrate restriction on fat oxidation can vary depending on a number of factors, including the intensity and duration of the exercise, the individual’s level of fitness, and their diet and training history.
For example, training in a carbohydrate-restricted state may increase the body’s ability to use fat as primary fuel source more efficiently, enhanced aerobic fitness by stimulating greater mitochondrial biogenesis (formation of mitochondria- the power house of cell), improved capillarization in the muscles fibres (oxidative quality of the muscles) and due to a higher fat us as fuel a decrease in muscle glycogen sparing/utilization (glycolytic power,VLamax) during exercise.
It may also increase the production of certain hormones that play a role in metabolism, such as human growth hormone (HGH):
Improved performance markers:
- increased FU (fractional utilisation of V02peak)
- improved aerobic capacity aka V02max
- increased lactate threshold
- improved muscular endurance
- reduced VLamax (=reduced lactate building rate)
- reduced rate of glycolysis at sub-maximal power outputs
Therefore, irrespective of whether fuel stores are a limiting factor (typically not the case for races less than ~2-3 hours, provided you refuel), RCA training might be beneficial by allowing you to perform at a higher power/pace for a given lactate level.
However, it is important to note that carbohydrate restriction may not be suitable for everyone and should be approached with caution.
Therefore, it is important to approach carbohydrate restriction with caution and to speak with your coach or sports nutritionist before making any significant changes to your diet or training routine.
For example, Relative energy deficiency in sport (RED-S) is a condition that occurs when an athlete does not consume enough energy (calories) to meet the demands of their training and competition.
This can lead to a number of negative consequences, including impaired physical performance, increased risk of injury, and negative impacts on health and well-being.
RED-S is a particular concern for athletes in weight-sensitive sports, such as wrestling, boxing, and gymnastics, where there is pressure to maintain a low body weight or body fat percentage.
However, it can also affect athletes in other sports, especially those who engage in excessive exercise or have disordered eating patterns.
The key to preventing RED-S is to ensure that athletes consume an adequate amount of energy to support their training and competition.
This may require working with a sports nutritionist to develop a personalized nutrition plan that meets the athlete’s specific energy and nutrient needs.
In addition, it is important for athletes to be aware of the signs and symptoms of RED-S, such as decreased performance, fatigue, and menstrual dysfunction, and to seek help if necessary.