Carb Cycling: How It Works

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Carb Cycling: How It Works
Carb Cycling

If you’ve reached a workout plateau, you might have researched different ways to overcome it and come across ‘carb cycling’. Carb cycling means increasing and decreasing the volume of carbohydrates you eat so you have ‘low-carb days’ and ‘high-carb days’.  

One benefit of carb cycling is that you can time your carbohydrate intake to fit in with your lifestyle — this means you can enjoy eating at celebrations and events while still staying focused on your nutrition and fitness goals!

What is carb cycling?

Carb cycling is when you vary the amount of carbohydrates that you eat at each meal, throughout the week or month to suit your lifestyle and maximise the fitness benefits of carbohydrate consumption. 

Carb cycling is used by some athletes to match their energy intake with their training schedule, with higher carb intake on training days and lower carb intake on rest days. 

When carb cycling is used in this way, it can help to maximise the quality of each training session by making energy from carbs readily available to the muscles during a workout and promoting faster muscle recovery after a workout. 

Another way carb cycling is used is to include scheduled ‘refeeds’ during a prolonged period of low carb intake. This helps to reset your body, and is especially important if you have been in a calorie deficit. Plus, you may be more likely to stick to your low-carb days when you have a high-carb day to look forward to.

When Should You Carb Cycle

Who is carb cycling for?

Carb cycling may be suitable for women with a goal to increase lean muscle, lose body fat or maximise their training and recovery. You might also try carb cycling if you’ve reached a plateau in your fitness progress.  

It does require substantial forward planning, so may not be suitable for every lifestyle. 

There isn’t much evidence that suggests carb cycling has significant fitness benefits compared to eating a healthy, balanced diet, taking regular rest days and following a progressive training program. 

Carb cycling is often used by athletes and bodybuilders with the goal of simultaneously burning fat and building muscle. 

It’s important to note that carb cycling is contraindicated for anyone who is pregnant, has diabetes or hypoglycemia. Carb cycling is also not recommended for people with a history of disordered eating. Always consult a healthcare professional before making any changes to your diet.

What should I eat when carb cycling?

On high-carb days, focus on eating complex carbohydrates. Complex carbohydrates contain more essential nutrients and fibre, and are found naturally in plant foods. You’ll aim to get around 50-70% of your nutrition from high-quality carbohydrate sources.

Sources of complex carbohydrates include: 

  • Sweet potato
  • Wholegrain rice 
  • Fruit
  • Oats
  • Quinoa

On low-carb days, you can still include a piece of fruit, but you will get more of your nutrition from nuts, vegetables with lower carb content like olives, tomatoes, spinach or kale, and protein sources like fish, chicken or eggs. Carbs will form around 20% of your nutrition intake. 

No-carb days may be used in some carb cycling regimes, depending on your nutrition and fitness goals. On these days, you aim to consume 50g of carbohydrate or less than 10% of your total energy intake. 

No-carb days are not recommended if you do high-intensity training, more than 30 minutes of cardio, or you need to be mentally focused, as you may have less energy and your ability to concentrate can be compromised when you eat a very low amount of carbohydrate. 

Increasing your portions of nuts, avocado or oily fish to include more healthy fats on low-carb days can help to keep you feeling satiated throughout the day.

Carb Cycling Benefits

How to use carb cycling to gain muscle mass

Carb cycling is one way to control how your body absorbs nutrients and stores energy. 

When you consume carbohydrates, glucose is released more quickly into the bloodstream, compared to other types of food. This spike in blood glucose increases the rate at which insulin is released into the bloodstream. 

Insulin is a hormone that is made in the pancreas in response to signals from your brain that food is being eaten. It helps to regulate your blood sugar by signalling the cells to absorb nutrients and energy from the bloodstream. 

By increasing the uptake of glucose and amino acids into muscle tissue, insulin also facilitates muscle repair and growth. 

On moderate and heavier training days, consuming carbohydrates along with protein will help to maximise muscle growth and recovery. 

On low-carb days, which generally coincide with a rest day if your goal is to gain muscle mass, insulin levels will generally not spike as high. This prevents your body from storing too much energy as fat. 

In this way, carb cycling can be used to promote muscle growth and minimise storage of energy as adipose tissue (fat) — exactly the result most of us are trying to achieve!

Benefits of carb cycling

Carb cycling may have health and fitness benefits when used as part of a balanced and holistic eating plan. 

Insulin sensitivity may improve

Insulin is a hormone that helps nutrients from food to move from your bloodstream to the cells of your body. When you eat, insulin is produced by the pancreas. As the food from your meal or snack is absorbed into the body, insulin levels in the blood decrease. 

High insulin sensitivity is when the cells of the body respond quickly to insulin in the bloodstream, absorbing nutrients to reduce blood sugar quickly after a meal. 

Low insulin sensitivity occurs if your cells don’t respond to high levels of insulin. Nutrients and sugars continue to circulate in the bloodstream for longer and insulin levels remain high for longer. 

Persistently high levels of insulin promote the storage of energy as glycogen (a readily available energy source in the muscles) and fat and can disrupt the production of leptin and other appetite-regulating hormones. 

Carb cycling to include days of low carbs can help your body to adjust its insulin response to food, improving insulin sensitivity and nutrient absorption. 

What Is Carb Cycling

Increased fat burning

Carb cycling can be one way to moderate your energy intake. This means that you might have a lower total energy intake on low-carb days and a higher total energy intake on high-carb days. 

Increasing insulin sensitivity can also promote fat-burning. High insulin levels in the blood encourage storage of blood glucose as fat. Increasing insulin sensitivity decreases the amount of time that insulin levels remain high and may reduce the amount of energy from food stored as fat. 

Risks of carb cycling

Reducing carbohydrate does come with some risks. You can minimise the impact of reducing carbohydrate intake by making informed decisions about what foods to include on low-carb days. 

Your brain runs on carbs

Even on low-carb days, you need to include some carbohydrate to help you stay alert and focused throughout the day. This can be from fruit or vegetables included in your low-carb meals and snacks

Your brain depends on glucose for fuel, a sugar produced when starchy foods are broken down by the body. It’s been shown that your brain may use more glucose during challenging mental tasks than it does at rest.

While the muscles of the body can use fatty acids as fuel when carbohydrate intake is low, the brain can only use glucose. When blood glucose levels drop too low, short-term memory and attention can be compromised. When glucose is introduced after a fast, memory improves. 

This means that eating regular meals with some carbohydrate can boost your mental performance. 

When there’s no carbohydrate available in your blood, your body may rely on other sources of glucose for the energy your brain needs, such as protein. This can be detrimental if one of your goals is building lean muscle. 

High Carb

Getting enough fibre on low-carb days

Lower carbohydrate intake can mean lower fibre intake when you reduce the amount of fruit and wholegrains in your diet. You can get fibre and important nutrients found in these foods from other sources, including cauliflower, broccoli and other cruciferous vegetables. 

Eating plenty of other high fibre foods and drinking water will minimise the consequences of reducing fibre from carbohydrates.

What to consider when carb cycling

When carb cycling, the types of food you choose to eat on your high-carb and low-carb days should help you to meet your overall nutritional requirements. 

The type of carbs you eat still matters

Even on your high-carb days, you should look for sources of carbohydrates that satisfy you and provide the nutrients that your body needs. 

For example, white bread and broccoli are both sources of carbs, but they are processed very differently by the body. Complex carbohydrates from whole food sources, like broccoli, contain fibre and important micronutrients to support your health and fitness goals. 

Highly-processed carbohydrates, like white bread, generally don’t have the nutritional value of complex carbs. Simple sugars in processed carbs are quickly absorbed into the body, causing a spike in insulin production.

This may be counterproductive if one of the benefits you want from carb cycling is to increase insulin sensitivity or reduction of body fat. 

Low Carb

Eat enough protein on high-carb days

Protein in your diet is critical for maintaining lean muscle. This means that you need to include high-protein foods in your meals and snacks even on your high-carb days!

Protein has a ‘high thermic effect’ which means that it takes a significant amount of energy to digest and absorb it into the body — about 10% of the energy from protein is used to metabolise it.

This means that including protein on your high-carb days can be done effectively without exceeding your energy requirements.

Carb cycling compared to keto

Both carb cycling and the keto diet involve reducing carbohydrate intake. So what makes these two eating plans different?

The keto diet allows for 20-50g of carbohydrate each day or 10% of the total energy intake. This very low carbohydrate intake causes the body to enter into ‘ketosis’, where the body uses stored fat as energy instead of glucose.  

During carb cycling, you won’t usually enter into ketosis. On low-carb days, your carbohydrate intake can be 50-150g. These carbs will usually come from non-starchy vegetables and dairy. 

A healthy, balanced diet is the most sustainable way to achieve your health and fitness goals! However, if you are curious to learn more about more regimented eating plans like carb cycling, keto, intermittent fasting or One Meal A Day, seek advice from a registered dietician who can provide guidance that’s specific to you and your training schedule. 

Carb cycling is one tool you can use as you work towards your fitness goals

There are many different approaches you can take to adapt the way you eat to suit your health and fitness goals. No matter what changes you want to make to your nutrition, the key to being healthy in the long term is to create sustainable healthy eating habits

Have you tried carb cycling? How did you go? Let us know in the comments below!

* Results may vary. Strict adherence to the nutrition and exercise guide are required for best results.

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