Carb cycling is the dietary eating pattern of alternating high and low carbohydrates. This is done by maintaining relatively the same protein and fat intake but adding in or taking out the number of starchy carbohydrates depending on your workout schedule. It is an eating pattern that bodybuilders and other athletes have used for a few decades.
This can be done in either a daily progression or a workout-specific progression.
Daily - It’s an alternating 4-5 days of low carbs and 2-3 days of high carbs.
Workout specific - Consuming carbohydrates before and after a workout but restricting it at other meals. Endurance athletes will aim for around 60 grams of carbohydrates during a session.
As there are few studies performed it is difficult to find a direct source as to what constitutes low and high carbohydrate parameters specifically for Carb Cycling. As this is a tactic that has been perpetuated by bodybuilding, the website Bodybuilding.com stated "1-1.5g/kg bw carbs on high days with a maximum of 200g of carbs".
Purported claims:
It is used to optimize energy intake to build muscle and lose fat.
It claims to avoid metabolic adaptation (fat loss plateaus and requirement to keep lowering caloric intake for fat loss) as the high carb days prevent the body from reducing its metabolic needs and leptin levels. By alternating the leptin response, this prevents starvation signals from occurring and preservation of fat reserves activating.
Insulin is another area activated when carbohydrates are consumed, leading to muscle and fat building. Alternating high carb days takes advantage of the muscle-building properties whilst preventing the fat-building properties. The low-carb days allow for insulin sensitivity to increase.
High-carb days are for high activity workouts when the body can run off glucose and replenish its glycogen stores. This includes high-quality vegetable starches such as sweet potatoes, plantains, bananas, squash, wild rice, lentils, oatmeal. Alternating carbs is viewed as a strategic re-feeding phase, whether it is alternating days or around workouts.
Low-carb days have a focus on healthy fats and protein with non-starchy vegetables. This includes fish, eggs, yogurt, broccoli, kale, leafy greens, cucumber, peppers.
If a weight-loss plateau occurs, it is stated that changing into either 3-4 carb-heavy days or 3 no carbs (including fibrous) will restart the fat-burning process. This is not based on scientific research, just anecdotal information.
What the science says:
There is very little research on this specific eating pattern. It has been around for decades, yet no detailed scientific studies have been recorded.
This is not a ketogenic diet as a state of ketosis takes 2-4 days to enter into and therefore this does not utilize ketones.
This is a cyclical movement of carb intake to have enough energy for workouts but decreases calorie intake on low-carb days leading to an overall deficit each week. Research into healthy adults with specific fat loss or muscle-building goals using carb cycling is almost non-existent.
Our take:
If your goal is to lose fat, then this may work for you for as long as you’re in a calorie deficit; your body will utilize your fat storage. If you’re able to sustain carb cycling as your means to do this, then it is a viable option.
However, this is an inflexible process of tracking that may be difficult for some to follow. It may also lead to feelings of guilt, failure, and mental exhaustion if the participant is unable to maintain this strict eating regimen.
A low-carbohydrate diet can also lead to low energy, fatigue, hormonal issues (especially in women), irregular menstrual cycles, difficulty regulating temperature, and other symptoms.
As of now, the lack of research into the carb cycling method and its claimed benefits make it difficult to decipher the difference in its approach from other low-carb diets.
Will this benefit you?
This process has minimal impact. Being conscious of carb refueling is important for a pro-athlete where every oz of muscle matters and multiple competitions occur in a day, so this eating pattern may aid them.
This process may also benefit women where intermittent fasting is detrimental due to hormone interruption from long-term calorie deficits.
But any eating pattern that requires diligent focus over a lifetime can be socially and mentally exhausting. It is unlikely for most people that a Carb Cycling program is needed. As with other fitness-specific eating patterns, this may not be a good long-term strategy, especially if unsupervised by a health professional.
Still curious to try it? If you do, here’s what to keep an eye on:
On high-intensity workout days, add in high starch carbohydrates such as sweet potatoes, potatoes, whole grains, beans, and lentils. If following a workout-specific carb cycle, add in these carbs post-exercise. Be careful to focus on nutrient-dense starches in order to get the right foods for your gut microbiome and nutrient requirements.
References and additional reading:
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