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A Complete Guide to Carbs & Carb Cycling

what is carb cycling

What is Carb Cycling?

When it comes to carbohydrates, one of our essential macronutrients, it is clear that they are misunderstood and feared by many.

Try going into any local fitness center, log onto any fitness website, talk to any nutrition expert, and you will receive a number of different thoughts and opinions on how much, which types, when to consume carbs, and all the possible health risks or rewards for eating carbohydrates.

What Are Carbohydrates?

Before we get to the definitive answers about carbs, let’s first define and breakdown what a carbohydrate actually is. The U.S National Library of Medicine has defined the term carbohydrates as:

“One of the main types of nutrients. They are the most important source of energy for your body. Your digestive system changes carbohydrates into glucose, blood sugar. Your body uses this sugar for energy for your cells, tissues and organs. It stores any extra sugar in your liver and muscles for when it is needed.”(1)

Carbohydrates are biological molecules made up of carbon, hydrogen, and oxygen in a ratio of roughly one carbon atom (C) to one water molecule (H2O). This chemical bond composition is where the origin of the name carbohydrate comes from.

Carbon (carbo-) plus water (-hydrate) = Carbohydrate

The rate at which our bodies are able to break carbohydrates down for readily available or stored energy depends on the different lengths of their chemical bond chains. Biologically, carbohydrates can belong to one of three possible sub-categories:

  • Monosaccharides – a single sugar molecule

  • Disaccharides – formed when two monosaccharides bond together

  • Polysaccharides – three or more sugar molecules bonded together

For the non-chemist, it is easier to categorize carbohydrates as one of two main types:

  • Simple carbohydrates – These are most commonly found as sugars in fruits, dairy, processed or refined foods and grains, syrups, sodas, and table sugars.

  • Complex carbohydrates – These are often found in the form of fibrous starches, like whole grain oatmeal, bread, pasta, rice, green leafy vegetables, potatoes, beans, lentils, corn, and peas.

Which Carbs Should We Be Eating?

The answer to this seemingly simple question has to begin with asking some more questions:

“Which carbohydrates are most easily digestible?”

“What time will you be training?”

The type of carbohydrate you need to eat revolves around these two factors: overall digestion and nutrient timing. Digestion is a key factor because it plays a vital role in almost every bodily process.

Carbohydrates are responsible for not only providing the body with energy, but also helping to increase fat oxidation, stimulate protein synthesis, and help with cellular recognition processes. It becomes imperative that we are able to make proper use of these nutrients through digestion.

People in the fitness and nutrition industries have strong and varying opinions about what kinds of carbohydrates to eat and when to eat them. Start a discussion about it and voices will be raised in heated debate.

So why are timing and type of carbohydrate consumption important and contentious?

How we digest carbohydrates, when we eat them, and the types we eat, all affect the production and storage of sugar in the body:

  • As blood sugar levels rise, the pancreas produces insulin, a hormone that prompts cells to absorb blood sugar for energy or storage.

  • As cells absorb blood sugar, levels in the bloodstream begin to fall.

  • When this happens, the pancreas starts making glucagon, a hormone that signals the liver to start releasing stored sugar.

  • This interplay of insulin and glucagon ensure that cells throughout the body, and especially in the brain, have a steady supply of blood sugar.(2)

So, in simple terms: simple carbohydrates will provide quick energy that can raise blood sugar levels quickly, while complex carbohydrates will provide a more sustainable energy source, keeping blood sugar levels stable for an extended period of time.

This is why nutrient timing, as well as type of carbohydrate, is important. Timing carbohydrates and choosing the right ones based on your training sessions can maximize health benefits, including improving athletic performance, enhancing recovery, and improving body composition.

For example, after finishing an intense training session, your body's carbohydrate tolerance will be higher due to muscle contractions increasing the facilitated depletion of glucose in the cells of your muscle tissue.

This depleted state allows for the absorption of more nutrients into the muscles, which otherwise would be stored as body fat, or adipose tissue.

At no other time during the course of the day can nutrition have such a profound impact on physique development and recovery as when the body is ready to shift to an anabolic state.

Through carbohydrate cycling via nutrient timing, you can maximize the post-workout hypersensitivity to insulin and prompt the desired results you're looking to achieve over time.

What Is Carb Cycling and Why Should I do it?

Carb cycling is essentially a nutritional protocol that aims to time carbohydrate consumption to when and where it will provide maximum benefits and to exclude carbs when they’re not needed.

This approach is most commonly used for those who are looking to lose weight, drop body fat, or rev up their stalled progress in the gym.

Carb cycling requires individuals to not only track, but rotate their carbohydrate intake through three types of days:

  • High-carb days: Consuming higher amounts of carbohydrates helps restore glycogen levels and spike insulin, which inhibits muscle breakdown, allowing you to maintain lean muscle tissue. The hardest training sessions should be performed either on, or the day after a high carb day, when glycogen stores are at their highest.

  • Medium-carb days: A moderate amount of carbohydrates helps maintain fuller glycogen stores and allows for sustained performance while being in a slight caloric deficit.

  • Low-carb days: These are typically rest days—when you supposedly "trick" your body into burning fat at an accelerated rate. Because the body doesn’t have glucose readily available for immediate energy, the body must turn to adipose tissue as a primary fuel source.

How to Start Carb Cycling

To start a carb cycling approach to carbohydrate consumption, you have to start with the number of calories you consume.

Track your food intake over the course of three to four days and total up the macronutrients—protein, carbohydrates, and fats—for a typical day. Do not change your eating patterns during this timeframe, as it will paint an unrealistic picture.

Once you have a summary total for all three macronutrient groups, you will be able to start right at step number four listed below.

If you don’t know what your caloric total is, you can use the steps below to get a rough baseline estimate of calories based upon your age, weight, and height.

Step #1: Calculate Your Basal Metabolic Rate

Your basal metabolic rate (BMR) simply means the amount of energy used by your body during a 24-hour period without considering any physical activity. In other words, if you're inactive for 24 hours straight, you still "burn" the amount of calories equivalent to your BMR. (3)

Your BMR is a sum of your age, weight, and height, which can be calculated with the Harris-Benedict formula:

  • For Men: BMR = 66 + (13.7 x weight in kg) + (5 x height in cm) - (6.8 x age)

  • For Women: BMR = 655 + (9.6 x weight in kg) + (1.7 x height in cm) - (4.7 x age)

Step #2: Daily Physical Activity Level

Now that you have your BMR, multiply it by a number that represents your current level of physical activity. (4)

Activity Level Factor

Activity Level




Very light activity


Light activity


Moderate activity


High activity


Extreme activity

Step #3: Determine Your Macronutrient Breakdown

Next you need to calculate approximately what portion of your calories comes from each of the macronutrients. For example, for a 175-lb. male with a daily caloric intake of 2,500 calories:

Protein = 1.15 grams per lb. x BW

(175 x 1.15 g per lb. = 201.25 g protein)

Fat = .30 grams per lb. x BW

(175 x.30 g per lb. = 52.5 g)

Each gram of protein accounts for four calories, so:

201 g of protein x 4 calories per gram = 804 calories

Each gram of fat accounts for nine calories, so:

53 g of fat x 9 calories per gram = 477 calories

Together, protein and fat account for 1281 calories of this hypothetical man’s calories.

This leaves a total of 1219 calories that come from carbohydrates. Divide this number by 4 (calories per gram of carbohydrate) and this man consumes 305g of carbohydrates per day.

The total macronutrient breakdown for a typical 175-pound man is 53 g fat, 305 g carbs, and 201 g of protein per day. Together these total his 2,500 calories per day.

Step #4: Determining Amounts for Cycling Carbs

To determine how many carbs you should be consuming on high, medium, and low carb days, follow these guidelines:

High-carb days – Maintain your current ratio of fat to carbs to protein: 53/305/201

Medium-carb days – Decrease your carb intake by 15 to 20 percent: 305 x .20% = 61 g. Decrease your carb intake from 305 to 244: 53/244/201

Low-carb days – Decrease your carb intake by 20 to 25 percent of the medium-carb day amount: 244 x .20 = 48 g. Decrease your carb intake from 244 to 196 grams: 53/196/201

Step #5 Adjust Macronutrient Amounts as Your Diet Progresses

Our bodies have been designed to adapt, so when trying to lose weight, you'll eventually need to lower your calories. Re-evaluate every three or four weeks and recalculate. To help with the evaluation of your plan, take pictures, body measurements, and scale weight to monitor progress.

Based upon your progression, you may need to evaluate a couple of KEY factors:

  1. What is the duration of your cardiovascular work? How many sessions a week are you completing? Remember, the key to promoting weight loss is expending more calories than you're taking in.

  1. Decrease carbohydrate calories slightly on your medium and low days to continue losing fat at an optimal rate. Avoid making drastic cuts. This is the reason most people lose muscle when they diet. Try dropping around 20 grams of carbs (for each “high”, “medium”, and “low” day) every two to four weeks.

What You’ll Get from Carb Cycling

Carb cycling puts you in a caloric deficit, but that means your body will begin to adapt. It will learn how to function on ‘X’ amount of calories to perform daily tasks and physical activities. The problem with this adaptation is not only that it slows down chemical reactions in the body, but it also downregulates your thyroid, which is responsible for fat loss. Leptin, the hormone that signals to your brain that you are full or satisfied, also downregulates as part of this adaptation.

In other words, simply cutting back on carbs and calories, over time, will stall weight loss.

This is the purpose of the higher carbohydrate days. You offset this natural adaptation process by boosting leptin levels and keeping your metabolic rate high.

To get some of the benefit of carb cycling, without going through the calculations, try a higher carbohydrate based meal. It will have the same effect, but will not be as precise since you are not strictly determining your carb amounts through calculations.

You will also need to remain “low-carb” for about six to ten days before having a higher carbohydrate based meal or the refeed day. Remember also that the term “low-carb” will be different for everyone. The elite athlete who has 6% body fat may very well think and “feel” that 150 grams of carbs per day is “low,” while the 9-5 sedentary office worker will have a low-carb day with just 50 grams.

When you have your refeed day after many days of following a low carb intake, drastically increase your carbohydrate consumption (five to ten times your current intake). Again, this is a general recommendation, but trainers working with clients regularly will be able to come up with a better guideline for each individual.

For a cheat meal, follow a few rules for optimal success:

  • Eat for no more than one hour at a time.

  • Make protein a big portion of this meal.

  • Increase the carbs and fats too.

  • Don’t feel guilty!

Personally, I usually go to an all-you-can-eat sushi place for my cheat meals and then stop somewhere on the way home for some ice cream. Another time, I may go grab a few burgers and fries from a place I like and then get a milkshake or some frozen yogurt afterwards. Whatever you’re craving, go for it; this is a time to mentally relax from the rigor of dieting and also reset your body into high fat-burning mode.

Carbohydrates: A Summary

There is a lot to remember when it comes to carb cycling, so here is a quick summary:

  • Weight Loss: Any dietary protocol that has you in a calorie deficit over an extended period of time will result in weight loss, regardless of the foods you eat, how you structure your meals, or any other variable.

  • Use lower calorie days to maximize fat burning.

  • Use higher- and medium-carb days to replenish glycogen stores and to increase training intensity.

  • Favorably influence various hormones related to muscle protein metabolism and fat metabolism.

  • Temporarily spike insulin levels to help preserve muscle tissue.

  • Increase insulin sensitivity. Allow the body to better utilize this hormone via total carbohydrate intake.

  • Above all else, be consistent.

Carb cycling is a great way to maximize fat loss, get over a plateau, and to feel better overall. If your client hits a plateau in fat loss, is getting bored with the current protocol, or has been very low-carb for a sustained period of time, suggest trying out a carb cycling approach as your next weapon in the fat loss arsenal.






DISCLAIMER: Thomas Munck is not a doctor or registered dietitian. The contents of this document should not be taken as medical advice. It is not intended to diagnose, treat, cure, or prevent any health problem - nor is it intended to replace the advice of a physician. Always consult your physician or qualified health professional on any matters regarding your health.



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