February, 2016
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Carbohydrate intake has been a hot topic for a long time.
While no macronutrient is categorically bad, carb intake is something that should be tailored to the individual (4).
In order to optimize carb intake, some people now “cycle” their carbohydrates.
This is known as carb cycling.
This article provides a detailed breakdown of the science and application of carb cycling.
What is Carb Cycling?
Carb cycling is a dietary approach in which you alternate carb intake on a daily, weekly or monthly basis.
It is commonly used to lose fat, maintain physical performance while dieting, or overcome a weight loss plateau.
Some people adjust their carb intake day-to-day, while others may do longer periods of low, moderate and high-carb diets.
In short, carb cycling aims to time carbohydrate intake to when it provides maximum benefit and exclude carbs when they’re not needed (5, 6).
You can program your carb intake based on a variety of factors, including:
- Body Composition Goals: Some will reduce carbs during a diet, then add them back during a “muscle building” or performance phase.
- Training and Rest Days: One popular approach is a higher carb intake on training days and a lower carb intake on rest days.
- Scheduled Refeeds: Another popular approach is to do 1 or several days at a very high-carb intake to act as a “refeed” during a prolonged diet.
- Special Events or Competitions: Athletes will often “carb load” prior to an event, and many physique competitors will do the same before a bodybuilding show or photoshoot.
- Type of Training: Individuals will tailor carb intake depending on the intensity and duration of a particular training session; the longer or more intense the training is, the more carbs they will consume and vice versa.
- Body Fat Levels: Many individuals will cycle their carbohydrates based on their level of body fat. The leaner they become, the more high-carb days or blocks they include.
A typical weekly carb cycling diet may include two high-carb days, two moderate-carb days and three low-carb days.
Protein intake is usually similar between days, whereas fat intake varies based on the carb intake.
A high-carb day normally means low-fat, whereas the low-carb days are high-fat.
Carb cycling is an advanced diet strategy requiring more manipulation and programming than a typical diet.
Bottom Line: Carb cycling is a dietary approach in which you manipulate carb intake depending on a variety of factors.
The Science Behind Carb Cycling
Carb cycling is a relatively new dietary approach.
The science is primarily based on the biological mechanisms behind carbohydrate manipulation.
Carb cycling tries to match the body’s need for calories or glucose. For example, it provides carbohydrates around the workout or on intense training days.
The high-carb days are also in place to refuel muscle glycogen, which may improve performance and reduce muscle breakdown (9, 10).
Strategic high-carb periods may also improve the function of the weight- and appetite-regulating hormones leptin and ghrelin (11, 12).
The low-carb days are reported to switch the body over to a predominantly fat-based energy system, which may improve metabolic flexibility and the body’s ability to burnfat as fuel in the long-term (8, 13).
The low-carb days and targeting of carbs around the workout may improve insulin sensitivity, a vital marker of health (15).
In theory, this approach will maximize the benefits carbohydrates provide.
Although the mechanisms behind carb cycling support its use, it should be interpreted with caution due to the lack of direct research on the approach.
Bottom Line: The proposed mechanism of carb cycling is to maximize the benefits of carbohydrates and teach the body to burn fat as fuel. While this makes sense in theory, more direct research is needed.
Can Carb Cycling Help You Lose Weight?
The mechanisms behind carb cycling suggest that it can be beneficial for weight loss.
In theory, carb cycling may help you maintain physical performance while providing some of the same benefits as a low-carb diet.
As with any diet, the main mechanism behind weight loss is a calorie deficit, as in eating less than your body burns over a prolonged period of time (16).
If a carb cycling diet is implemented alongside a calorie deficit, then you will likely lose weight.
However, its more complex nature may cause adherence issues and confusion for beginners.
In contrast, many people may enjoy the flexibility of carb cycling. This could probably improve adherence and long-term success for some people.
Bottom Line: Carb cycling can help you lose weight as long as you maintain a calorie deficit. Eating plenty of protein can be useful as well.
Carb Cycling for Muscle Growth and Sports Performance
Many people believe that carb cycling can be beneficial for muscle gain and physical performance.
The regular high-carb periods and targeted carb intake may help improve performance (17).
Carbs around the workout may also aid with recovery, nutrient delivery and glycogen replenishment (9, 10).
This may also promote muscle growth. However, some research suggests carbs are not needed to build muscle if protein intake is sufficient (18).
While these mechanisms make sense in theory, direct research comparing carb cycling to other diets is needed to provide an evidence-based answer.
Bottom Line: The mechanisms behind carb cycling suggest it can help you optimize performance. However, further research is required.
Does Carb Cycling Have Any Other Benefits?
As already mentioned, carb cycling has the potential to provide some benefits that other diets cannot.
By having periods of low and high-carb, you may get many of the benefits provided by both diets, without some of the negatives.
Benefits of low-carb periods may include better insulin sensitivity, increased fat burning, improved cholesterol and enhanced metabolic health (8, 13, 15, 19, 20).
High-carb refeeds may also have positive effects on hormones during a diet, including thyroid hormones, testosterone and leptin (12, 21).
These factors may play an important role in long-term dieting success, since hormones play a key role in hunger, metabolism and exercise performance (22).
Bottom Line: Low-carb periods may provide a number of health benefits, and high-carb refeeds can have positive effects on your hormones.
How to do Carb Cycling
There are many variations to carb cycling, including daily alterations or longer periods of high and low-carb cycles.
Here is a sample week where you regulate your carb intake on a daily basis:
Even more so than a regular diet, carb cycling can take a lot of fine tuning and adjustment along the way.
Experiment with the amount of high-carb days per week, as well as the amount of carbs per day. Find the best approach for your lifestyle, exercise routine and goals.
If you prefer a low-carb diet, you can add carb cycling occasionally in the form of a refeed. Here are some sample low-carb plans with occasional high-carb blocks:
As the table suggests, you can either refeed every couple of weeks or do long periods, such as a 4 week low-carb phase, with a 1 week refeed.
You will also notice the amount of carbs per day can drastically vary – this depends on activity level, muscle mass and carbohydrate tolerance.
An athlete who trains 3 hours a day or a 250 lb bodybuilder may need the upper limit (or even more), whereas a normal individual may only need to refeed on 150-200g.
Finally, these examples are suggestions only. There is no proven formula or ratio for carb cycling and you should tailor and experiment with it yourself.
Bottom Line: There are several options for carb cycling, ranging from daily changes to monthly refeeds. Experiment to figure out what works best for you and your goals.
Example Carb Cycling Menu
Here are three sample meal plans for low-, moderate- and high-carb days.
High-Carb Day
- Breakfast: 3 boiled eggs, 3 slices Ezekiel (or 7 seed/grain) bread, tomatoes, mushrooms and a side bowl of mixed fruit (60 g carbs).
- Lunch: 6 oz sweet potato, 6 oz lean meat or fish, mixed vegetables (45 g carbs).
- Pre-Workout: 1 serving oatmeal, almond milk, 1 cup berries, 1 scoop whey protein (50 g carbs).
- Dinner: 1 serving wholemeal rice, 6 oz lean chicken, homemade tomato sauce, 1 serving kidney beans, mixed vegetables (70 g carbs).
Moderate-Carb Day
- Breakfast: Grass-fed high-protein yogurt, 1 cup mixed berries, stevia, 1 spoon seed mix (25 g carbs).
- Lunch: 6 oz chicken salad with 4 oz diced potatoes (25 g carbs).
- Pre-Workout: 1 banana with whey protein shake (30 g carbs).
- Dinner: 1 serving sweet potato fries, 6 oz lean beef, homemade tomato sauce, 1 serving kidney beans, mixed vegetables (40 g carbs).
Low-Carb Day
- Breakfast: 3 eggs with 3 slices bacon and mixed vegetables (10 g carbs).
- Lunch: 6 oz salmon salad with 1 spoon olive oil (10 g carbs).
- Snack: 1 oz mixed nuts with 1 serving turkey slices (10 g carbs).
- Dinner: 6 oz steak, half avocado, mixed vegetables (16 g carbs).
Recommended Carbohydrate Food Sources
Some carbohydrates should be avoided, except on special occasions or for the occasional treat.
In contrast, there are plenty of healthy carb sources that are tasty and packed full of beneficial fiber, vitamins and minerals.
When planning your high-carb days, do not use it as an excuse for an all-out pop-tart binge. Instead, focus on these healthier carb choices.
Recommended “Good” Carbs:
- Whole Grains: Unmodified grains are perfectly healthy and linked with many health benefits. Sources include: brown rice, oats and quinoa.
- Vegetables: Every vegetable has a different vitamin and mineral content, eat a variety of colors to get a good balance.
- Unprocessed Fruits: As with vegetables, every fruit is unique, especially berries with their high antioxidant content and low glycemic load.
- Legumes: A great choice of slow digesting carbohydrates, which are full of fiber and minerals. Just make sure you prepare them properly.
- Tubers: Potatoes, sweet potatoes, etc.
Bottom Line: High-carb days are not an excuse to binge on junk food. Instead, eat mostly healthy whole-food sources of carbs.
Summary
Carb cycling may be a useful tool for those trying to optimize their diet, physical performance and health.
The individual mechanisms behind carb cycling are supported by research. However, no direct research has investigated a long-term carb cycling diet.
Rather than chronic low or high-carb diets, a balance between the two may be beneficial from both a physiological and psychological perspective.
If using carb cycling for fat loss, ensure that your protein intake is adequate and you maintain a calorie deficit.
Always experiment with the protocol and amounts of carbohydrates to find the best fit for you.
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