Carb Cycling - The Muscle PhD

Carb Cycling

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In this piece we’re going to offer a general overview on carb cycling as there are a ton of variables at play and we just don’t have time to go super in-depth with each component. Nutrition is always a touchy subject so it’s worth sticking to an objective view as much as possible to give the most well-rounded information. We’ll touch a little on some various strategies for cycling and we’ll also explain some loopholes in the research that leave a lot of the decision making up to you.

First thing’s first, carbohydrates are the primary energy source we use during training as they are stored as glycogen in both muscle and the liver and are readily used for energy. Intense endurance training will rely on carbohydrates for fuel to a greater degree than resistance training, but lifting weights can definitely still cause a decent amount of glycogen depletion (15,23). Altering the glycogen content of the muscle before, during, or after training, then, may induce different training adaptations. Enter, carb cycling.

Carb cycling is simply a strategy for rotating high, low, and moderate carbohydrate days. There are a few different ways to do this which we’ll cover throughout the article. Carb cycling first became popular in endurance training as it was shown to potentially enhance adaptations to endurance exercise (11,17). This caused some researchers to even ponder if carb cycling was the key to optimal training adaptations in endurance athletes (6). All of these findings are due to the fact that muscle glycogen storage can act both as a fuel for training and as a signaling pathway to promote adaptations to training (1). Muscle glycogen content can also modulate transcription factors that may affect the protein synthesis process (17) – this may contain some unique applications in resistance training.

So now that we have the general idea on what carb cycling is, what benefits have been found in the research?

Benefits of Carb Cycling

One of the major components of carb cycling is that you’ll perform some workouts in a glycogen-depleted state. Training in a glycogen-depleted state has been shown to enhance the expression of genes that promote the creation of mitochondria (6,9,27,28). Increasing mitochondrial density in the muscle cell can improve the energy efficiency of the muscle cell, increase fat oxidation, and improve endurance performance (14,17). This major finding has led to many researchers looking further into this phenomenon to optimize endurance training adaptations, and has caused others to ponder its use for general health as well.

Now, we know from the Fasted Training article (read here) that the occasional fasted training session might not do much for fat burning, but research has shown that adopting a carb cycling plan in accordance with specific training strategies can increase fat loss compared to non-carb cycling diets in as little as 3-weeks (16). This is probably due to both the increase in fat oxidation during exercise (14) and the increase in mitochondrial density from low carb training.

So why is all of this the case? Didn’t we all learn in school that consuming carbs before your workout was necessary for optimal performance and gains? The theory is that training in a low carb state can actually increase the physiological stress of the workout (12). As we’ll touch more on later, most carb cycling strategies involve performing your lower volume/intensity workouts in a low carb state. Performing lower volume workouts in a low carb state may still induce higher levels of training stress and promote similar levels of adaptation without crushing you like a super high-volume workout would.

These strategies can be perfect for individuals who periodize their training throughout the week with high, moderate, and low volume workouts. So, let’s get into the various methods of carb cycling and how you can use them in your own training.

Methods of Carb Cycling

1. Train High, Sleep Low, Train Low, Repeat

The title of this one is a real mouthful and it’s definitely a strategy that would require a significant volume wave in your training. Essentially, to make this strategy work you would have to alternate high volume and low volume days throughout the week. With that being said, let’s get into it.

This method is one of the most heavily-researched in endurance sports because alternating high and low training volumes on a day-to-day basis is extremely popular in endurance training. The easiest way to visualize this is to imagine a typical training week. On Monday, you’re going to do a high volume, crusher of a leg workout, because that’s the best way to start the week, right? This workout would represent your, “Train High,” workout because it’s high volume and longer in duration. So, you eat carbs throughout the day before your workout so your glycogen stores are fully ready to go when it’s time to hit the weights. However, once your workout is over, you’re done eating carbs for the day – this represents the, “Sleep Low,” portion of the title. The idea is to extend the period of glycogen depletion following training, as this may promote further adaptation (17).

The next step is to perform your Tuesday workout in a low carb state, i.e. the, “Train Low,” step. This Tuesday workout should be a shorter workout with less volume and less overall intensity – doing a steady state cardio session or even an arms session would be a good idea here. As soon as this session is over, you can start eating carbs again to restore muscle glycogen stores (17). You essentially skip out on carbs from the minute you finish your, “Train High,” workout all the way to the end of your, “Train Low,” session.

And finally, the last step is to, “Repeat,” the cycle. Your Wednesday workout can be another bone crusher in which you consume carbs beforehand to optimize training volume and intensity, but once the workout is over, you’re done consuming carbs until after the next lighter workout or cardio session (17). Like we already said, to optimally perform this method, you’d have to alternate high and low volume days to still get the most out of each session.

One caveat to this strategy is that resistance training recovery does have different requirements than endurance training recovery, so we would strongly suggest increasing your protein intake to account for fewer carbs following your heavy workouts (26). Protein without carbohydrates can still maximally increase protein synthesis rates (13) and consuming protein without carbohydrates post-workout has been shown to offer similar gains in the long term compared to protein + carbs (8).

2. Fuel for the Work Required

Another popular method for carb cycling is called, “Fuel for the Work Required.” This method is a little easier to plan out as most bodybuilders or powerlifters aren’t always going to perfectly alternate high volume and low volume sessions. In short, this method simply involves planning out your carb intake based on how your training is going to be that day (6). So, for high volume leg days in which you’re training hard for at least an hour, you’re going to want to have a high carb day to support that training. On upper body days that aren’t quite as challenging as lower body days, you could probably get away with a moderate carb intake. And finally, on rest days or cardio days, going low carb will be best as you don’t have any intense training to fuel.

This is, by far, the most flexible method and what we would assume to be the most popular method of carb cycling in strength athletes. This creates a scenario in which you’re always fueling appropriately for your training on that day – this helps avoid both spilling over on carbs but also avoids undereating carbs which may impair training performance during longer workouts (5).

One additional component that many can add to this method is the, “Sleep Low,” approach from above. This would essentially include always sleeping on low carb stores but would be highly dependent on the time of day you train (12). This method would work best for those who train at night, because those who train in the morning will have a much tougher time avoiding carbs throughout an entire day. Like we discuss above, this, “Sleep Low,” period can extend the amount of time your muscles spend in a glycogen-depleted state which can boost mitochondrial density and fat burning in the long term.

3. Two-a-Days

One last method that can be super beneficial to bodybuilders on a cut is, “Two-a-Days.” Now, we know that many bodybuilders undergoing a cut will start their day off with a fasted cardio session then do their lifting workout later in the day. What if you reversed that? Studies have shown that performing a heavier/higher volume session in the morning, avoiding carbs all day, and then doing a lighter session in the evening while carb-depleted can increase whole body fat burning (6,18,28).

For starters, this is partly due to the fact that the first workout is performed in a, “fed,” state in which muscle glycogen content is at least moderate. Studies show that increasing carbohydrate utilization during a workout can actually increase fat burning the rest of the day (21). Combining that strategy with a carb-depleted workout at night can be a great method to maximize fat burning.

The best part is that you can still eat carbs after your evening session – you don’t necessarily have to, “Sleep Low,” on this method. This is due to the fact that since your heavy workout is in the morning, eating some carbs before bed can help increase muscle glycogen content for that heavy workout. As you can tell, most carb cycling methods all essentially end up at, “Fuel for the Work Required.” Fuel your heavy workouts, and stay on the lower end for lighter sessions.

One last interesting component to carb cycling is that ramping up carb intake to about 600g per day for 3 days have been shown to significantly increase lean mass due to increased muscle glycogen storage (24). This strategy may even be furthered in effectiveness if performed after a few lower carb days, so this can be a solid method for growing into a contest or just getting a solid pump for a weekend at the beach.

Are There Any Downsides to Carb Cycling?

A major issue that we see with carb cycling studies is that many of them simply don’t last long enough to show if there’s long term performance benefits to carb cycling. We see short term performance benefits with carb cycling (6,16,17,28) but most of these studies are 3-weeks in length or less (16,17,28). Other studies that show changes in gene expressions are acute studies, meaning that they simply examined one or a few training sessions (7). Changes in gene expression would obviously influence long term adaptation, but we still don’t have many longitudinal studies.

Another shortcoming with the research on carb cycling that we touched on earlier is that literally all of it has been performed on endurance training. Endurance athletes are looking to promote different gains than strength athletes, so increasing expression of certain genes or signals isn’t always the goal of strength athletes. Bodybuilders and powerlifters can all benefit from increased mitochondrial density and fat burning, however, so there is still certainly a place for it in the mass monster community – just maybe not to the same degree as endurance athletes.

In addition, the latest research into carb cycling is concerned with discovering the, “sweet spot,” for muscle glycogen levels and exercise adaptations (11). This is due to the fact that consuming a consistently high carbohydrate diet can reduce certain gene expressions and impair insulin sensitivity (22) but eating a consistently low carb diet can also restrict protein synthesis pathways (10). Therefore, we don’t have all of the answers yet on what the, “best,” carb cycling plan may be, but it certainly seems that there is a sweet spot for carb consumption and that cycling carb intake may help you stay in that sweet spot.

Another issue with carb cycling is that your low carb training sessions may not be the best training stimulus since carb-depletion can reduce training volume and intensity (3,4,5,20). Glycogen restriction may promote adaptations that are favorable for endurance athletes, but performing a training session without optimal energy levels can impair the training stimulus of a resistance training workout which can negatively affect gains. This represents a scenario in which carb cycling should be used as a tool rather than a law. If you’re in an intense gaining phase, you might want to limit your lower carb days to rest days. You’ll want to make sure you have appropriate carb levels to fuel longer, high volume workouts to maximize your training – and in a gaining phase, just about every workout is going to be like that.

Lastly, intense training in a glycogen-restricted state can increase your susceptibility to illness (2), so placing your low carb days appropriately is necessary for staving off illness while training hard. It may take a while to get adapted to a carb cycling plan, so always plan accordingly to place your low carb days with your low requirement days and vice-versa.


The research into carb cycling is still emerging and, frankly, not all of it applies to strength athletes. We know that intense lifting sessions can burn through a good chunk of muscle glycogen stores (15,23) so appropriating carbs for training intensity can definitely still apply to lifting weights. In addition, many of the adaptations that are thought to occur through carb cycling will be more beneficial for endurance athletes than strength athletes – we still need studies on carb cycling in strength athletes to determine potential benefits.

Ultimately, carb cycling is similar to periodizing your training. Your goal is to plan out variation in your nutrition to support an ultimate goal way down the road. Unfortunately, long term nutrition planning can be very tricky and is almost entirely dependent on what kind of training you are doing each day (12). I think the easiest way to plan your carb intake is to do so in accordance with your training plan – fuel your training, promote recovery, but don’t spill over on days that you don’t need many carbs. As long as your carb intake is supporting your goal for that day, you’ll be fine (19).

Carb cycling can also be a great way to modulate the quality of weight loss or weight gain depending on your goals. From the aforementioned studies finding positive effects on fat burning and fat loss, using carb cycling as a strategy to minimize fat gain during a bulk or maximize fat loss during a cut is a smart idea. The performance implications definitely paint one part of the picture, but body composition effects also play a massive role in bodybuilding.

We have known since at least 1887 that nutrition can strongly influence both performance and gains (25). However, optimal nutrition is almost entirely subjective to the individual. Eat to support your goals and adjust accordingly to how you feel and react to certain strategies. Many factors are in play when considering nutrition and just about every person is going to react differently to a diet – much like a training program, some people will be high responders and others won’t respond at all. No training plan is one-size-fits-all and neither is one diet. Try out the methods in this piece and see if they work for you.


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