Ultimate Bodybuilder's Carb Cycling Guide for Muscle Growth & Fat Loss

Bodybuilder's Carb Cycling Guide to Muscle Growth and Fat Loss by Justin Harris

What Is Carb Cycling?

Carb cycling is an approach to dieting that maximizes the effects of improving body composition within the boundary conditions of thermodynamics. Optimizing the use of specific macronutrients on certain days and times allows you to eat in a deficit for periods when glycogen stores are saturated to burn body fat while minimizing the risk of muscle loss. Those excess calories are then stored as glycogen rather than fat, allowing you to eat in a deficit for periods when glycogen stores are saturated to minimize the risk of muscle loss.

The result is an improved body composition over a period compared to the same net calorie total from a non-cycled macronutrient profile.

 Thermodynamics Calories


A calorie is simply a measure of energy. 

It is the amount of energy required to raise one gram of water by one degree Celsius. The calories you see listed on food labels are kilocalories, denoted with a capital “C” as “calories.”

“At the end of the day, whether or not you lose weight depends on the number of calories you consume vs. the number of calories you burn.” 

It’s as simple as that.

If this doesn’t seem to hold water for you, consider this—the law of conservation of energy is one of the most powerful laws of physics. Every physicist hopes to disprove it—because violating the law of conservation of energy even once is a guaranteed Nobel prize. Even better, it would mean an immediate solution to the world energy crisis via “free energy.”

If all that matters is how many calories are eaten vs. how many calories are burned, then why don’t we simply count calories and let that be the end of it? 

The reason is that total Calorie count only tells us what your total body mass will be—NOT what the composition of that mass will be. In order to affect body composition within a specific Calorie range, we need to consider the ratio of macronutrients in those calories. 

Macronutrients Protein


We know that the body stores excess calories as energy in the body. Those calories can be stored in three different forms:

  1. Adipose Tissue (body fat)
  2. Glycogen (glucose)
  3. Protein (muscle tissue)

Although macronutrients can be converted to different forms in the body through processes like gluconeogenesis, in general, the storage of calories can be viewed in this manner:

  1. Protein can be stored as muscle
  2. Carbohydrates can be stored as muscle and liver glycogen
  3. Fats can be stored as fats (any excess calories can be stored as fat)

How we divide our daily calories into macros dictates how the calories we consume are stored and used by the body. The goal is to minimize the amount of energy stored as fat while maximizing the amount of excess energy stored as glycogen and muscle. 


Protein is the most important macro for building muscle. In fact, it is the only macro that can be converted to muscle. To store new muscle you need a stimulus for protein synthesis (training), which will then allow new muscle tissue to be built if all 20 amino acids are available at the site of protein synthesis. Of these 20 amino acids, 9 of them MUST come from the diet. 

“Protein—more specifically amino acids—is the only macronutrient that can be converted to new muscle tissue.”

Since this stimulus can occur at any time, it is important to have a consistent supply of complete protein sources in the diet to foster muscle growth and prevent muscle loss. 


Carbohydrates are the primary fuel for weight training. 

When training with weights or doing cardio, the body will pull from glycogen—which is the form in which carbohydrates are stored in the body—for energy. If you eat too many carbohydrates, you will store the excess as fats. If you eat too few, the body will become glycogen-depleted and break down muscle tissue to create glycogen through gluconeogenesis. Because of this, proper carbohydrate timing is essential in an adequate nutrition plan—whether the goal is fat loss or muscle gain. 


Fats are the most efficient energy source in the body. 

Fats contain more than twice as much energy per gram as protein or carbohydrates and are essential to a performance diet. Fats promote proper hormone levels, healthy skin and slow down digestion to provide satiety and consistent energy metabolism.

 Bodybuilder Checking Time On Watch

Macronutrient Timing

The timing of specific macronutrients helps dictate whether those macronutrients will be utilized. 

Proper macronutrient timing can mean that excess calories are stored in the body as glycogen for training fuel later on and as muscle tissue for larger muscle mass. Improper macronutrient timing can mean that excess calories are stored as body fat. 

“The SAME Calorie intake that could lead to new muscle mass could also lead to new fat stores if the macronutrients aren’t properly timed.”

Macronutrient Timing - Muscle Growth

For muscle growth to occur, an excess of calories is consistently consumed—to maximize the amount of those excess calories stored as new muscle tissue and glycogen while minimizing the amount stored as fat. 

Protein Timing – Muscle Growth

Since muscle growth is a slow process—certainly much slower than fat loss—it becomes tedious to balance the need for excess calories for muscle growth with taking in too many calories and storing fat. It takes more than just extra calories to fuel muscle growth. The macronutrients those calories are composed of must be precisely timed. 

“Muscle growth is a slow process. A growth rate of only a ½ lb. of muscle per week results in 75 lbs. of new muscle in three years.”

Since a diet focused on muscle growth will have a higher total Calorie count, there is less potential that the protein included in those calories will be needed for energy and broken down to glucose via gluconeogenesis. Because of this, protein intake can be kept slightly lower in muscle growth diets. 

Enough protein must be consumed to ensure that amino acids are available during protein synthesis or muscle breakdown. Still, since a muscular growth rate of 25 lbs. per year results in only about 30-35g of new muscle built daily, it becomes clear that most of the protein you eat each day isn’t being converted to new muscle. 

“A growth rate of 25 lbs. of muscle per year is caused by converting only 30-35g of protein to muscle per day.”

So, rather than blindly increasing the amount of protein we eat, we need to MAXIMIZE the amount of protein converted to new muscle. To do this, we need to make sure that gluconeogenesis is minimized and amino acid uptake is maximized when protein synthesis is about to occur. 

Carbohydrate Timing - Muscle Growth

Since protein synthesis rates are most likely to be highest around a workout, it becomes important to intake higher amounts of carbohydrates around the workout. This ensures that the protein eaten at this time is available for the synthesis of new muscle rather than being converted to glucose for energy. 

“Consuming higher amounts of carbohydrates around weight training helps maximize the restoration of lost glycogen burned during training while maximizing the amount of protein that is available for new protein synthesis.”

Macronutrient Timing – Fat Loss

For fat loss to occur, more calories must be burned than are consumed. This results in the body releasing stored calories/energy to compensate for the missing calories in the diet. The goal is to minimize the amount of stored energy from muscle tissue and glycogen while maximizing the amount of energy burned from fat stores. 

Carbohydrate Timing – Fat Loss

With carbohydrates kept low during a fat-loss diet, optimizing the timing of the carbohydrates you eat becomes important. This is done by focusing the highest concentration of carbohydrates in the meals around the weight training workout. This increases insulin levels slightly around the time of weight training—when muscle breakdown is highest. 

The benefit of elevated insulin levels around the workout when muscle breakdown occurs is that insulin promotes amino acid uptake by the tissues. This helps maximize the likelihood that the proper amino acids are available to repair damaged muscle tissue before muscle loss can occur. 

Insulin also promotes glycogen storage. Following a workout, muscle glycogen levels will be in their most depleted state as muscle glycogen will be a primary energy source for the training session. To prevent a severe depletion of these necessary glycogen stores, the body will attempt to replace lost glycogen as much as possible.

Suppose glucose is unavailable in the bloodstream for this process. In that case, the body will create glucose—through gluconeogenesis—either converting dietary protein into glucose or, worse, breaking down precious muscle tissue to produce glucose. Having the majority of the day’s carbohydrates available for digestion at this time minimizes this effect. 

Protein Timing – Fat Loss

The only way of storing protein in the body for later use is as muscle tissue—and because we never want to break down the hard-earned muscle we’ve built—we want to make sure that there is a consistent supply of blood amino acids available at all times in the body.

The stimulus for protein synthesis can occur at any time, and of the 20 amino acids involved in the synthesis, 9 of them MUST come from the diet, we need to consume frequent doses of protein to ensure that the body maintains a positive nitrogen balance at all times.

Because of this, every meal consumed should contain some source of complete protein. 

Fat timing – Fat Loss

Fat is only stored as fat when excess calories are consumed (like all macronutrients). Still, when excess calories ARE consumed, fat is included in the macronutrients of excess calories—those fat calories will be preferentially stored as adipose tissue. Because of this, we need to be careful of our fat intake in meals where we’re actively looking to create glycogen storage through a Calorie surplus. 

 Carbohydrates Cycling

Carb Cycling

The most effective way to promote muscle growth and fat loss is to properly time and cycle the three macronutrients to optimize your nutritional goals. 

Carb Cycling for Fat Loss

In a fat loss program, protein will remain high so that any signal for muscle loss is blunted because there are elevated blood amino acid levels to create glucose from when needed. 

Protein also has the highest Thermic Effect of Food (TEF) and promotes Dietary Induced Thermogenesis (DIT) more than the other macros. 

Protein isn’t as readily usable as an energy source in its macronutrient form as carbohydrates or fat. Before it can be used as energy (outside of some direct energy use by branched-chain amino acids), protein must be converted first to amino acids or ammonia, and then to glucose, and if it isn’t used for energy as glucose, eventually to fat. These conversions require work by the body—up to 20-35% of the calories in protein are spent during these processes.

“Up to 20-35% of the calories in protein is BURNED in the process of digestion—this is called the Thermic Effect of Food (TEF)” The TEF for protein is another reason why it is becoming more important to maintain high protein levels on a fat loss diet."

Since protein is kept high in a fat-loss diet and calories are restricted, it becomes necessary to keep dietary carbohydrates and fats down. To slow digestion, minimize blood sugar swings, and increase satiety, healthy fats are consumed at as high of a level as allowed by one’s basal metabolic rate (BMR). 

With proteins and fats kept as high as possible, this typically means that carbohydrates are included in minimal amounts on most days. This is where the cycling and timing of the macronutrients become important.

 Woman Fat Loss from Carb Cycling Diet

Carb Cycling for Fat Loss (Continued)

With carbohydrate intake reduced on a fat loss diet and muscle glycogen stores chronically low, this presents a situation where a “metabolic boost” can be created, where one purposely eats more calories than they burn with the INTENTION of storing those excess calories in the body. However, when those excess calories come from carbohydrate sources in a glycogen-depleted state, you create a situation where those excess calories are stored as glycogen instead of fat.

In this situation, one can eat more calories than they burn without getting fat! The body still stores the excess calories, but they are stored as muscle glycogen instead of fat. 

This presents the case where a relatively large Calorie surplus can be eaten—providing MAJOR metabolism-boosting benefits—without the risk of ruining the fat loss goals of the diet. 

To break it down by the numbers, we’ll look at a case of a typical “gym rat” male with approximately 200 lbs. of lean body mass. This person will likely be able to store upwards of 800g of glycogen at maximum glycogen storage levels. If we consider them depleted in glycogen to only having 300g of glycogen remaining, then that gives us 500g of additional glycogen storage.

With the TEF for carbohydrates being around 10%, this gives us somewhere about 550g of carbohydrates ABOVE normal, which we can add to the diet for a “high carb day.” If we assume that this person will burn through roughly 100-200g of carbohydrates in their normal metabolic rate for the day—then this gives us as much as 750g of carbohydrates or a WHOPPING 3,000 calories that we can add ABOVE the normal daily Calorie intake for a single day of glycogen restoration and metabolism boosting. 

 Male Bodybuilder Carb Cycling Diet for Muscle Growth

Carb Cycling for Muscle Growth

When focusing on muscle growth, the cycling of macronutrients daily becomes less dramatic. Because muscle growth is a slower process than fat loss, Calorie surpluses in a muscle growth diet will be less severe than the Calorie deficits of a fat loss diet. Whereas a fat loss rate of 2-3 lbs. per week is possible on a fat loss diet—which requires a 1,000-1,500 daily Calorie deficit, a muscle growth rate of even ½ lbs. per week is on the extreme high end of what one can expect to achieve long term. 

Similarly to what is done on a fat-loss diet, some level of glycogen depletion is allowed and expected in a muscle growth diet. The remedy is the same in this case as in the fat loss plan—“high carb” days. In the offseason, this high-carb day becomes more about maximizing amino acid uptake through elevated insulin levels than restoring depleted glycogen levels. Still, the approach remains the same—one to three days of higher carbohydrate intake focused around the days when the largest body parts are trained and the highest level of protein synthesis will be triggered.

“In the offseason, ‘high carb days’ are more about maximizing amino acid uptake through the chronic elevation of insulin levels than over-saturation of glycogen stores in the muscles.”

Protein Cycling – Muscle Growth

Like fat loss, frequent and consistent protein intake is the most effective method for maximizing muscle growth. All 20 amino acids must be present at the site of protein synthesis before the new muscle can be made. 9 of those 20 amino acids must come from the diet. A protein source that contains all nine essential amino acids is called a complete protein.

“A protein source is called a ‘complete protein’ if it contains all nine essential amino acids.”

Because we’re looking for complete protein sources, our proteins in muscle growth diets should be centered around lean meat sources (chicken, fish, lean beef, turkey) and other complete proteins like egg protein and the most common protein powders. However, since our focus is on consistently elevated blood amino levels to allow for the synthesis of new protein whenever triggered, we want to minimize our use of protein powders in most cases. 

Quickly digesting protein powders rapidly spike blood amino levels, causing spikes much higher than the rate of protein synthesis could ever occur. The result is that high amounts of quickly digesting proteins like powders are converted to glucose through gluconeogenesis and then used as a carbohydrate—or worse—stored as body fat (as a muscle growth diet contains more calories than are burned).

Carb Cycling Diet Plan E-Books by Justin Harris

Expert-Designed Carb Cycling Diet Plans

I have used my 20 years of high-level education, research, and real-life experience to create in-depth mass-gaining and shredding programs (digital downloads) using a carb cycling approach. Both programs include a diet plan, food list, meal plan, and more. When fully customized, these programs adjust the diet plan based on your changing weight and lean body mass.

Achieve your optimal body mass, build muscle, and increase strength with expert support! Want to read more research and educational articles written by Justin Harris and Team Troponin? Visit our blog!


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