How To Use Carb Cycling To Lose Fat Or Build Muscle

One of the more popular “tools” for bodybuilders looking to achieve that peak condition for a contest is that of carbohydrate cycling. While calorie control is the first priority when it comes to your diet, macronutrient manipulation (e.g. carb cycling) is sort of the “next level” when looking to improve your physique.

While of course not everyone reading this is looking to step on stage and show off their shredded glutes, it is still useful for “everyday gym rats” to consider carb cycling as a method of dieting. Therefore, this article will discuss what exactly carb cycling is, who should consider implementing it, the physiological reasoning for it, and how to setup your own basic carb-cycling diet.

The Basics of Carbohydrate Cycling

It’s probably rather intuitive to most people that carbohydrate cycling is simply altering your total carbohydrate intake on given days. The general notation for denoting the amount of carbs to be ingested on certain days is usually along these lines:

No-Carb Days (or “Zero Starch” days)—the word “no” in this case means you aim to take in no starch or other direct carb sources. It is acceptable (and likely) that you will still ingest some carbohydrates from vegetables and certain fat sources, but the amount should be rather trivial (e.g. <5% of your total calorie intake).

Lower-Carb Days—As a general starting point, lower-carb days should have you shooting for 1g of carbohydrate per every pound of bodyweight (if you’re significantly over-fat it’s likely best to use your “lean body mass” instead).

Higher-Carb Days—these days are sort of the “refeed” portion of your diet. A good starting point for higher-carb days is to ingest at least 2g per pound of bodyweight (again, if you’re significantly over-fat consider using lean body mass).

NOTE*--the actual amount of carbs you take in on lower-/higher-carb days will need some fine tuning and we will address how to go about that later in the article

Given the nature of dieting being relative, it is impractical to apply a preset, all-encompassing quantity of carbohydrates to these categories. Thus, a more pragmatic approach is to use these categories as guides based on your bodyweight, as is indicated above.

Can I Use Carb Cycling To Build Lean Muscle?

Many people assume carb cycling only has merit when one is trying to shed the extra flab (e.g. is in a caloric/energy deficit), but I would actually argue that one would stand to benefit from carb cycling regardless of calorie intake. Reason being is that when someone is looking to add muscle without adding too much fat, it is useful to cycle carb intake in a fashion that allows for efficient muscle growth but at the same time limits carbs periodically to prevent unnecessary fat gains.

Likewise, when trying to lose fat (and spare muscle), one would want to cycle carb intake so as to optimize their fat-loss efforts while limiting the amount of muscle mass that is lost. So just because you’re “bulking” or “cutting” doesn’t mean you can’t implement carb cycling, and it’s actually useful in both scenarios.

What Carb Cycling Does Physiologically

Carb cycling, in a nutshell, acts as a means of regulating your endocrine system (and thus metabolic rate). Keep in mind that when you expose yourself to aggressive, chronic energy deprivation, your body compensates by lowering the demand for energy (e.g. metabolic rate slows).

Lowering metabolic rate is a basic survival mechanism in many organisms since it is counterproductive for an organism to be burning through energy rapidly without much nourishment available. Contrary to popular belief, if your goal is fat loss, it is not favorable to metabolically efficient. You actually want the converse—to be as metabolically inefficient as possible (essentially this means you require a greater amount of energy/have an increased metabolic rate).

The most notable endocrine alterations associated with chronic energy deprivation is the lowering of thyroid hormones and the adipokine leptin.[1,2] This impacts your metabolic rate for two reasons: first, leptin’s primary role is regulating metabolic expenditure as well as caloric intake, both of which have obvious implications with regards to bodyweight. Second, thyroid hormones (thryonines) act on practically every cell in the body to increase metabolic rate.

This is why carb cycling comes in handy during such instances, since carbs specifically have been shown to have significant stimulatory effect on metabolic rate, thyroid function, and leptin production (even in the short term).[3,4,5]

Therefore, the prudent solution to avoid diet-and exercise-induced metabolic slowing is to increase energy intake (especially carbohydrates) acutely to help revive hormonal and metabolic factors. This is why many bodybuilders dieting for a contest will actually increase their calorie intake when there fat loss stalls (i.e. they incorporate high-carbohydrate re-feeds).

Assessing Individual Carb Tolerances

Given the intricacies of metabolism and environmental factors that vary from one individual to the next, it is imperative that people realize what works for other individuals may or may not work for themselves when it comes to dieting.

Carbohydrates are arguably the most misunderstood and vilified macronutrient. They seem to get the short end of the stick because many people have a diet composed largely of simple sugars while concurrently remaining highly sedentary.

In essence, these individuals are constantly elevating blood glucose levels and not using the energy for anything; much of the excess ends up being stored and eventually converted to adipose tissue. This in turn manifests itself into type-II diabetes due to impaired insulin sensitivity from all the blood glucose fluctuation.

Naturally, people figure they will just cut back (or practically eliminate) carbs altogether and all will be well. I would rather argue that carbs shouldn’t be eradicated from your diet, but just controlled/cycled. Research does indicate that overweight individuals are susceptible to impaired insulin response, so yes, too many carbs can be an issue. But the trick is to keep carbs as high as possible while simultaneously achieving sufficient weight/fat loss or muscle growth, depending on your goal.

Therefore, the carb intakes that were suggested earlier in this guide serve merely as starting points. If you’re someone who is highly insulin sensitive and active, then it is likely you will require a greater carb intake than someone who has poor insulin sensitivity and sits around all day.

Don’t fear carbs (or any macronutrient for that matter), just use your head and be pragmatic about it; if you’re sitting at a desk all day and driving to work, then you probably should eat fewer carbs then someone who is active and on their feet all day.

The Glycemic Load -- Does Carb Source Matter?

Another common topic of concern when it comes to carbohydrates is the glycemic load. Carbohydrates that cause a large, rapid increase in blood sugar have a higher glycemic index and vice versa. The glycemic load is the overall, combined impact of a meal on one’s blood sugar.

Thus, the glycemic index in and of itself is not very practical when a complete meal is ingested; the aggressive insulinogenic activity that certain simple sugars induce will be altered when you combine them with other food sources.

Given this, eating simple sugars is not really a “bad” thing so long as you ingest other nutrient/foods that tame the glycemic load of the meal (like fiber, complex carbohydrates, unsaturated fats, leafy vegetables, etc.) This isn’t to say your sole source of carbohydrates should be pure dextrose, but just iterates the point that some sugar is fine and won’t magically make you gain weight.

The one exception to consider is that fructose (often found in fruits) does not exhibit insulinogenic activity, which may be counterproductive on higher-carb days. Moreover, fructose, unlike glucose, is predominantly metabolized in the liver (and thus replenishes liver glycogen, not muscle glycogen). Again, don’t take this to mean you can’t have any fructose (or simple sugars), just keep them within reason (say <25% of total carb intake).

Why Some Insulin is Important

Many individuals seem to have this irrational fear of insulin like even the tiniest amount of it will turn them into Butterbean. Frankly, insulin is actually your ally if you’re looking to optimize muscle hypertrophy. Numerous studies have verified that the MPS response to a nominal dose of amino acids can be enhanced by the presence of sufficient carbohydrate intake (and thus an increased insulin response).[6,7]

As addressed earlier with regards to individual tolerances, the key is to ingest a “sufficient” dose of carbohydrates to promote a nominal insulin response, but there is certainly no need too binge on a bunch of simple carbohydrates in an effort to ramp up insulin as high as possible. Insulin, in the physiological range, does not enhance the MPS response to meals in a linear fashion like many people believe. [8]

Fat Intake on Carb Cycling

Contrary to a typical keto diet which usually compensates for the restricted carb intake by greatly elevating fat intake, for someone on a carb cycling regimen this is not a very wise idea on no-/lower-carb days (nor higher-carb days for that matter).

Reason being is that chronic exorbitant fat intake  (especially saturated fatty acids) may induce insulin and leptin resistance and other metabolic maladies. [1,9] Essentially you are priming your fat cells (not your muscle tissue) to soak up all the carbohydrates your body takes in.

It is therefore advised to watch your fat intake while following a carb-cycling diet, and it’s not necessary to compensate for a dip in caloric intake (due to reduced carb intake) by loading up on fat sources.

How About Protein Intake While Carb Cycling?

Generally protein intake should be fairly static, but it may help to bump up intake a bit on no-/lower-carb days just to get some extra calories (this is especially important for those using carb cycling to build mass).

It is not necessary to load up on protein on higher-carb days, and due to the protein-sparing effect of carbohydrates you could probably get away with less protein intake.

Setting Up A Carb-Cycling Diet

The main “rule” to consider when carb-cycling is to not have consecutive higher-carb days in your rotation. The other “rule” (or suggestion rather) is to have your higher-carb days on your toughest/highest volume training days of the week; keep no-/lower-carb days for lighter training days, cardio days, and rest days.

Now that we’ve covered the basics of carb cycling and the physiological reasoning behind it, let’s layout a few sample programs for individuals based on the goal at hand. There are actually many ways to go about setting up your carb-cycling diet so just use the rules laid out herein as guides when creating your regimen.

Goal: Fat loss

NOTE*--N=No-carb day, L=Lower-carb day, H=Higher-carb day

• No-carb Days—2 per week
• Lower-carb Days—3 per week
• Higher-carb Days—2 per week

Sample Diet Rotation (Starting on Monday)—L,L,N,H,L,N,H

--So with the rotation above, this individual would ideally have their toughest/highest-volume training days on Thursday and Sunday of each week. Depending on their training regimen, they should keep Wednesday and Saturday as cardio days (or off days) and the rest of the week could be for “lighter” resistance training days.

Goal: Fat loss (and isn’t very insulin sensitive)

NOTE*--N=No-carb day, L=Lower-carb day, H=Higher-carb day

• No-carb Days—3 per week
• Lower-carb Days—3 per week
• Higher-carb Days—1 per week

Sample Diet Rotation (Starting on Monday)—N,L,N,H,L,N,L

Goal: Muscle gain

NOTE*--N=No-carb day, L=Lower-carb day, H=Higher-carb day

• No-carb Days—1 per week
• Lower-carb Days—3 per week
• Higher-carb Days—3 per week

Sample Diet Rotation (Starting on Monday)—L,H,N,H,L,L,H

Goal: Muscle Gain (and is highly insulin sensitive)

NOTE*--N=No-carb day, L=Lower-carb day, H=Higher-carb day

• No-carb Days—0 per week
• Lower-carb Days—4 per week
• Higher-carb Days—3 per week

Sample Diet Rotation (Starting on Monday)—H,L,H,L,L,H,L

Wrap Up

As you can see there are really many possible ways to setup a carb-cycling diet and much of it will depend on your training regimen, goal and tolerance for carbohydrates. Again, the information in this article is meant to guide you while creating your carb-cycling regimen. Try out a few rotations and adjust as needed; optimizing your diet entails trial-and-error. Don’t be discouraged when something doesn’t go as planned, but instead, use it to progress and learn from.

References:

1) Ahren, B., Mansson, S., Gingerich, R. L., & Havel, P. J. (1997). Regulation of plasma leptin in mice: influence of age, high-fat diet, and fasting. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology,273(1), R113-R120.

2) Krotkiewski, M., Toss, L., Björntorp, P., & Holm, G. (1981). The effect of a very-low-calorie diet with and without chronic exercise on thyroid and sex hormones, plasma proteins, oxygen uptake, insulin and c peptide concentrations in obese women. International journal of obesity, 5(3), 287.

3) Jenkins, A. B., Markovic, T. P., Fleury, A., & Campbell, L. V. (1997). Carbohydrate intake and short-term regulation of leptin in humans.Diabetologia, 40(3), 348-351.

4) Dirlewanger, M., Vetta, V. D., Guenat, E., Battilana, P., Seematter, G., Schneiter, P., ... & Tappy, L. (2000). Effects of short-term carbohydrate or fat overfeeding on energy expenditure and plasma leptin concentrations in healthy female subjects. International journal of obesity, 24(11), 1413-1418.

5) Mathieson, R. A., Walberg, J. L., Gwazdauskas, F. C., Hinkle, D. E., & Gregg, J. M. (1986). The effect of varying carbohydrate content of a very-low-caloric diet on resting metabolic rate and thyroid hormones. Metabolism, 35(5), 394-398.

6) O'Connor, P. M., Bush, J. A., Suryawan, A., Nguyen, H. V., & Davis, T. A. (2003). Insulin and amino acids independently stimulate skeletal muscle protein synthesis in neonatal pigs. American Journal of Physiology-Endocrinology And Metabolism, 284(1), E110-E119.

7) Kimball, S. R., Jurasinski, C. V., Lawrence, J. C., & Jefferson, L. S. (1997). Insulin stimulates protein synthesis in skeletal muscle by enhancing the association of eIF-4E and eIF-4G. American Journal of Physiology-Cell Physiology, 272(2), C754-C759.

8) Koopman, R., Beelen, M., Stellingwerff, T., Pennings, B., Saris, W. H., Kies, A. K., ... & Van Loon, L. J. (2007). Coingestion of carbohydrate with protein does not further augment postexercise muscle protein synthesis. American Journal of Physiology-Endocrinology And Metabolism, 293(3), E833-E842.

9) Kraegen, E. W., Clark, P. W., Jenkins, A. B., Daley, E. A., Chisholm, D. J., & Storlien, L. H. (1991). Development of muscle insulin resistance after liver insulin resistance in high-fat–fed rats. Diabetes, 40(11), 1397-1403.