Shaun Ward MSc ANutr
A lot of successful diets revolve around the restriction of carbohydrates and some even eliminate their intake completely.
Whilst carbohydrates are not an essential nutrient for health, they should by no means be categorized as “bad”.
The best approach is to tailor carbohydrate intake to each individual, depending on their activity levels, training goals, physique and performance goals, and personal preferences.
However, even at an individual level, the requirement for carbohydrate often changes day to day, or week to week, as these determining factors change.
This is where the idea behind carbohydrate cycling was introduced, as it allows for different amounts of carbohydrates to be consumed as required.
What Exactly Is Carb Cycling?
Carbohydrate cycling is a dietary approach in which people alternate carbohydrate intake on either a daily, weekly, or monthly basis.
The reasons for doing so are usually only relevant for people who have training, physique, or performance goals.
At its core, carbohydrate cycling is a means by which to match the personal and metabolic need for this energy source on a daily basis.
Some common examples are:
- People wanting to lose body fat will gradually decrease their carbohydrate intake each week to ensure continuous energy deprivation and fat loss.
- Athletes with different amounts of training each day will increase or decrease their carbohydrate intake dependent on the needs of that day
Based on this, carbohydrate cycling is not a low, moderate, or high carbohydrate diet, it is them all encompassed into one.
This makes carbohydrate cycling an advanced dietary strategy which requires far more manipulation and programming than a typical diet.
Outside of carbohydrate intake, daily protein intake will usually stay consistent day to day, whilst fat may be increased on low carbohydrate days to compensate for the reduced energy intake (and vice versa).
The Benefits of Carb Cycling
Here are the main reasons to carb cycle and how to do it effectively:
It Can Improve Your Endurance
Carbohydrates are necessary to best perform during high-intensity exercise.
Research shows that deliberately training with reduced carbohydrate availability can successfully enhance the metabolic adaptations of skeletal muscle needed for endurance.
This idea started the concept of “train low, compete high”, where endurance athletes would strategically lower their carbohydrate intake during training periods to improve adaptation, but ensure high carbohydrate intake during competitive events to perform optimally.
When compared with high carbohydrate availability, data shows low carbohydrate availability may augment cell signaling, gene expression, and oxidative enzyme activity/protein content in a manner which improves an athletes endurance capacity.
The primary benefit behind these metabolic adaptations appears to be the increased ability to burn fat during exercise, which enables an endurance athlete to spare carbohydrate stores for later use when the intensity of exercise is inevitably increased due to fatigue  .
Such knowledge has also led to new concept of “fuel for the work required”, whereby carbohydrate availability is adjusted in accordance with the demands of the upcoming training session.
However, the main potential issue with carbohydrate cycling in this context is how it should be strategically implemented.
The challenge is to quantify the carbohydrate requirements of a given training session to simultaneously ensure absolute training intensity is not compromised, while also benefitting from the enhanced metabolic responses that are favorable by training with reduced carbohydrate availability .
It is worth noting that such a nutrition protocol should not be used in sports based around strength and power training, as low carbohydrates will ultimately reduce both training adaptations and performance.
It Can Improve Your Athletic Performance
On the other side of things, carbohydrate cycling can also help improve performance when needed, such as in competition.
This is based on the facts that carbohydrates are the required fuel source to support high-intensity activity, as well as the depletion of carbohydrates being the point at which fatigue tends to begin.
The main reason why is because the depletion of carbohydrate stores (muscle glycogen) will negatively influence the flux of calcium in muscle tissue and impair the contractile property of the muscle .
Unfortunately when carbohydrate stores become depleted, the up-regulation of fatty acid oxidation is unable to cover the high demands for energy synthesis required for high-intensity activity .
By increasing carbohydrate intake – and carbohydrate stores – leading into an event, you can increase the length of time at which you can perform to a high-intensity.
The nature of carbohydrate-loading strategies vary based on the exact demands of the event in question, however the benefits of carbohydrate loading are generally only seen in events lasting longer than 90 minutes – the point at which carbohydrate stores will typically become depleted.
Standard carbohydrate loading strategies recommend the intake of 8-12 grams of carbohydrates per kilogram of bodyweight in the 24 hour period before a competitive event begins.
It Can Improve Your Body Composition
Carbohydrate is the only macronutrient with no established minimum requirement for health.
This makes it the most flexible macronutrient, as despite it not being essential for health, it is important to maximize performance.
Based on this, for people on a weight loss phase, carbohydrates are typically the main nutrient that will first be reduced due to its lesser role for maintaining health compared to dietary protein and fat.
However, carbohydrates still play their part during a weight loss phase as they can help to maintain performance levels whilst dieting. The logical implication of this is to increase carbohydrate intake on training days, and to reduce carbohydrate on intake on rest days.
In addition, the strategic use of weekly or bi-weekly carbohydrate “refeeds” is a method used by physique competitors. There are 2 main reasons for this:
- Increase the production of satiety hormones: This is based on evidence indicating that leptin is acutely responsive to short-term overfeeding, and highly correlated with carbohydrate intake .
- Stimulate metabolic rate: Carbohydrate refeeds may acutely increase total daily energy expenditure by 5-10% (~100-200kcal per day) .
Overall, using such a method may be able to reverse many of the unfavorable adaptations of prolonged calorie restriction .
Based on survey results from competitive bodybuilders, they mention positive outcomes of “refeed” days including improved training performance, mental recovery, preventing downgrades in energy expenditure, and further stimulating weight loss. One participant even described it as a “metabolic jumpstart” .
The scientific confirmation behind such a theory is yet to be seen, however it is certainly a valid concept on paper that seems to be having success in practice.
It Can Improve Insulin Sensitivity
Insulin sensitivity describes how sensitive the body is to the presence of insulin, and thereby describes how well an individual can tolerate eating carbohydrates.
A person with good insulin sensitivity will require less insulin to adequately transport glucose from the blood and into cells compared to someone with poor insulin sensitivity.
Insulin resistance describes when a state where a person has an impaired cellular response to insulin, resulting in elevated levels of glucose remaining in the blood for long periods.
Unsurprisingly, the number 1 cause of insulin resistance is the frequent and excessive consumption of carbohydrates that results in a diminished sensitivity to insulin over time – eventually resulting in diabetes  .
The combination of insulin resistance and hyperinsulinemia also disrupts fat metabolism and increases the risk of cardiovascular disease, the most common source of mortality among individuals with diabetic complications .
In contrast, when dietary carbohydrate is restricted and blood sugar levels are more stable, this provides a metabolic state that ultimately avoids lipotoxic processes that impair β-cell function and insulin secretion.
Considering this, a great component of carbohydrate cycling is the manipulation of insulin. It allows people to schedule the consumption of carbohydrates around exercise when these carbohydrates will be quickly used for energy purposes as opposed to staying in the blood.
This allows for the control and manipulation of both carbohydrate intake and insulin secretion on a daily basis to give the best results regarding the avoidance of developing insulin resistance .
The idea behind carbohydrate cycling is to alternate the amounts of carbohydrates consumed over a set period, in order to accelerate changes in body composition and performance.
This nutritional approach is highly complex, but it has many benefits that a lot of elite athletes are taking advantage of.
The main benefits to carbohydrate cycling, when done correctly, are improved body composition, performance, endurance training adaptations, and even insulin sensitivity.
People who are really “all-in” to optimize their nutrition should look to incorporate carbohydrate cycling.