The Science of Carb Cycling: How It Works and How to Do It Right

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IF YOU WANT TO KNOW WHAT CARB CYCLING IS, HOW IT WORKS, AND WHETHER YOU SHOULD DO IT OR NOT, THEN YOU WANT TO READ THIS ARTICLE.

I don’t know about you, but I like simple.

And here’s a simple fact for you:

You don’t need to do anything particularly special or fancy to build the body of your dreams.

At least 80% of the game is just understanding and applying a relatively small number of physiological principles related to diet and exercise.

And I’d go as far as saying that the majority of what’s left is just patience and persistence.

You don’t need convoluted training programs or diets. You needfundamentals.

That said, once you have the fundamentals firmly in place, you can look to gain slight edges.

This is where things like supplementation, fasted training, periodization, and carb cycling come into play.

In this article, we’re going to dive deep into carb cycling and learn what it is, how it (supposedly) works, and how to do it.

We’re also going to review many of the fundamentals that supercede it, and ultimately, we’re going to get an answer to the most important question:

Is carb cycling better than traditional dieting?

That is, can it really beat the simplest way to diet?

Let’s get to it.

What is Carb Cycling?

carb cycling

Carb cycling is a method of dieting that involves planned increases and decreases in carbohydrate intake (and generally in caloric intake as well).

There are many different carb cycling protocols, but most have you alternate between at least two of three types of days:

  • High-carb days

High-carb days typically call for 2 to 2.5 grams of carbohydrate per pound of body weight. They are usually your highest calorie days.

  • Low-carb days

Low-carb days typically call for about 0.5 grams of carbohydrate per pound of body weight. They are usually your second-highest calorie days.

  • No-carb days

No-carb days typically call for less than 30 grams of carbohydrate. They are usually your lowest calorie days.

If all that sounds complicated to you, that’s because, as far as dietary strategies go, it is. You need to be meticulous in your meal planning and steadfast in your compliance.

Many people find it physically and mentally taxing as well. This meme pretty much sums it up:

carb cycling meme

So, if carb cycling has a lot of moving parts and may turn you into a manic depressive, why do people do it?

How Does Carb Cycling Work?

how does carb cycling work

We’re often told that carbs are a double-edged sword.

The story goes like this:

  • On one hand, they’re conducive to muscle growth by fueling our workouts and creating a more anabolic environment in our bodies.
  • On the other hand, they’re conducive to fat storage by spiking insulin levels, which “feeds” our body fat with precious glucose for it to store.

Thus, a predicament:

We need carbs if we want to build muscle and strength as quickly as possible…but we have to pay the price of an ever-expanding waistline.

Or do we?

Enter carb cycling, which we’re told can deliver most or all of carbs’ muscle-building benefits with little or none of its fat gain drawbacks.

It accomplishes this rather staggering feat by using higher-calorie high-carb days to do several things:

  • Replenish glycogen stores and thus bolster training intensity.
  • Favorably influence various hormones related to muscle protein metabolism and metabolism.
  • Temporarily spike insulin levels to help preserve muscle tissue.

And by using lower-calorie low- and no-carb days to maximize fat burning.

How carb cycling (supposedly) helps you build muscle and lose fat at the same time:

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Theoretically, then, this should allow us to build muscle while gaining little to no fat or, even better, build muscle and lose fat at the same time.

And now you understand why carb cycling is so popular these days. It sounds like a miracle.

Unfortunately, though, upon closer inspection, it’s more a mirage.

To find out why, let’s start with carb cycling’s biggest claim to fame: rapid fat loss.

Is Carb Cycling Good for Weight Loss?

carb cycling for weight loss

Can you use carb cycling to lose weight?

Absolutely.

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 or how you structure your meals or anything else.

Or, put more simply:

So long as you regularly eat less energy than you burn, you’re going to lose weight.

So long as you regularly eat less energy than you burn, you’re going to lose weight.

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That said, carb cycling isn’t sold as “just another way” to lose weight.

It’s the way to lose weight. The “secret” of the fitness elite and “best way to drop pounds fast.”

And that’s when the wheels start to fall off.

To understand why, we have to first make a distinction between weight loss and fat loss.

When you diet to lose weight, a portion of the weight lost comes from fat, but a portion also comes from water, glycogen, and, in some cases, muscle.

Water and glycogen levels will fluctuate up and down depending on your diet and other factors, so we don’t really care about that. The real goal is to lose fat and not muscle. That’s what improves our body composition.

What does this have to do with carb cycling, you wonder?

Well, at its core, carb cycling is a carbohydrate-restricted diet, and while it may help you loseweight faster, it isn’t going to help you lose fat faster.

That is, if a traditional “40/40/20” bodybuilding diet would have you eating, let’s say, 1,500 grams of carbohydrate per week, a carb cycling diet might peg your intake at half that or less.

And while low-carb diets can, in the short term, beat out traditional diets in terms of weight loss (but not always), they don’t result in greater fat loss.

Yes, you read that right.

Low-carb diets are not better for fat loss than their higher-carb counterparts.

Low-carb diets are not better for fat loss than their higher-carb counterparts.

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Sure, there are exceptions (certain metabolic disorders and extreme obesity, for example), but the above holds true for the vast majority of people.

If that sounds blasphemous to you, I understand, but a sober review of the literature makes this abundantly clear.

Low-carb advocates often have a stable of studies to bandy about as definitive proof of the superiority of their ways.

This, this, and this are fan favorites.

A glib review of such studies would lead you to believe that low-carb dieting is indeed more effective for fat loss, but a critical review of the research shows otherwise.

There’s a big problem with many of these studies, and it has to do withprotein intake.

Namely, the low-carb diets in these studies invariably contained more protein than the high(er)-carb ones.

That means that what we’re actually looking at is a high-protein, low-carb diet vs. a low-protein, higher-carb diet…and the former will result in more weight and fat loss every time.

Why is that, though? Is it because the carb intake is lower or because the protein intake is higher?

Well, there are several studies that answer that question for us.

Research shows that when protein intake is high and matched among low- and high-carb diets, there is no significant difference in weight loss.

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That is, if you eat enough protein, going low-carb as well offers no special fat loss benefits.

How can that be, you wonder? What’s so special about protein?

Several things actually.

The Power of Protein

carb cycling food list

One of protein’s weight loss advantages has to do with something known as the thermic effect of food,or TEF.

This is the amount of energy required to eat, digest, absorb, and store food, and research shows that it accounts for about 10% of total daily energy expenditure.

The total energy expenditure from TEF varies based on the macronutrient composition of the diet because protein, carbohydrate, and dietary fat all have different TEF values.

Research shows that protein costs the most energy to process (30 to 35%), carbohydrate costs significantly less (5 to 15%), and dietary fat costs the least (3 to 4%).

This is one of the reasons why high-protein diets are so effective for fat loss (it’s also why high-fat meals result in more immediate body fat gain than high-carb meals).

You see, when a considerable amount of your daily calories come from protein, a considerable amount of that energy is expended through TEF, which helps you maintain a calorie deficit.

Another reason for protein’s preeminence is the fact that eating too little while dieting to lose fat can result in a considerable amount of muscle loss.

This, in turn, hampers your fat loss in several ways:

  1. It causes your basal metabolic rate to drop.
  2. It reduces the amount of calories you burn in your workouts.
  3. It impairs the metabolism of the food you eat.

The bottom line is this:

If you want the best possible results when dieting to lose fat, you want to eat plenty of protein.

If you want the best possible results when dieting to lose fat, you want to eat plenty of protein.

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With that in mind, let’s swivel our spotlight back to the flawed low-carb studies I mentioned earlier.

We already know that the low-carb groups were eating more protein than the high-carbers, but how much more exactly?

Well, in many cases, the high-carb groups were eating far less–less than even the RDI of 0.8 grams per kilogram of body weight, which studies have shown is woefully inadequate for preserving lean mass. In fact, research shows thatdouble and even triple the RDI amount isn’t enough.

So, given all the above, we shouldn’t be surprised that high-protein, low-carb diets are superior for weight loss compared to low-protein, high-carb diets.

You might still be reeling from the fact that high-protein, high-carb diets work equally well, though.

Don’t carbs spike insulin levels, and doesn’t insulin spike fat storage?

Well, while that’s a physiologically accurate statement, it’s used to mislead millions of people into fearing insulin and carbs.

The Bogeyman of Insulin

does carb cycling work

One of the easiest ways to invent a fad diet is to isolate some aspect of eating and hang everything else on it.

For the low-carb crowd, insulin is the great bugaboo; the evil hormone programmed to make us fat, type 2 diabetics.

And the carbohydrate, we’re told, is insulin’s trojan horse and partner in crime. We eat the delicious carbs, and they open the insulin floodgates and chaos ensues.

Or something. Don’t look into it. Just buy my pills and PDFs. PLEASE.

Well, like much of the nonsense foisted on us by magazines, trainers, and “gurus,” the “insulin makes us fat” story is nothing but an urban legend used to scare the kiddies.

Insulin doesn’t make you fat. Overeating does.

Insulin doesn’t make you fat. Overeating does.

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To understand why this is, let’s jump to square one: what is insulin and how does it work?

Well, insulin is a hormone that shuttles nutrients from your blood to your cells.

When you eat food, it gets broken down into various substances like amino acids, glucose, and fatty acids. These all make their way into your bloodstream, and are joined by insulin, which is produced by the pancreas. As the nutrients make their way into cells, your body gradually reduces insulin levels until everything is absorbed. Insulin then remains at a low, baseline level.

This cycle occurs every time you eat food, and thus your body’s insulin levels are constantly rising and falling throughout the day.

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Now, when explained like that, insulin sounds like a pretty cool dude. We can’t live without it. Why, then, are we told it makes us fat and sick?

Well, because one of its roles in the body relates to fat storage, and that makes it an easy target.

Specifically, insulin inhibits the breakdown of fat cells and stimulates the creation of body fat. That is, it tells the body to…

  1. Stop burning fat and burn the energy readily available from the food you ate instead.
  2. Store a portion of the energy that’s available as body fat.

And yes, that sounds bad, which is why it’s an easy target and scapegoat.

The “logic” goes like this:

High-carb diet = high insulin levels = burn less fat and store more = get fatter and fatter

And then, as a corollary:

Low-carb diet = low insulin levels = burn more fat and store less = stay lean

This sounds reasonable but is deeply flawed, mainly because it violates the principles of energy balance.

Energy balance is the relationship between how much energy you eat and how much you burn.

This relationship determines weight change over time and takes precedence over anything related to insulin or any other hormones.

Simply put, you can’t gain a significant amount of fat without providing your body with a surplus of energy to store as fat. And you can’t lose a significant amount of fat without keeping your body in a significant energy deficit, forcing it to whittle down its fat stores to stay alive.

This helps us understand why studies show that, so long as protein intake is matched, people lose fat equally well on high-carb and low-carb diets.

The takeaway is simple: if there’s an adequate calorie deficit, carbohydrate intake and insulin levels have little bearing on fat loss.

The ne plus ultra of this scientific reality is Professor Mark Haub’s weight loss experiment wherein he lost 27 pounds on a “convenience store diet” consisting mainly of protein shakes, Twinkies, Little Debbie cakes, Doritos, and Oreos.

He fed his body less energy than it burned and it had no choice but to tap into its fat stores, regardless of how unwholesome the food was.

It’s also ironic to note that eating protein, which we already know is conducive to weight loss, significantly raises insulin levels as well.

In fact, high-protein, low-carb meals can cause more insulin production than high-carb meals, and beef produces a similar insulin response to brown rice.

So, now that you know why low-carb dieting doesn’t burn fat faster, you know the answer to the following question:

Does carb cycling help you lose fat faster?

The answer is no, of course, because eating fewer carbs on some days and more on others (and eating fewer in general) isn’t going to significantly impact your fat loss. The two factors that aregoing to are your protein intake and energy balance.

That said, this doesn’t necessarily mean you shouldn’t cycle your carbs when you want to lose weight.

Some people’s bodies don’t process carbs well and respond better to lower-carb dieting. You generally see this in people that are very overweight, and in these cases, carb cycling can serve them well.

Another reason to carb cycle when you want to lose weight is because you like it. It might not offer any metabolic advantages but it doesn’t harm anything either, so if it’s going to help you keep your diet on track, that’s valuable.

Is Carb Cycling Good for Building Muscle?

carb cycling for muscle gain

This is going to sound familiar:

Can you use carb cycling to build muscle?

Absolutely.

So long as you’re eating enough food and you know what you’re doing in the gym, you can build muscle.

Does carb cycling offer any special muscle-building benefits, though?

Unfortunately, it doesn’t. In fact, it’s less suitable for building muscle than traditional dieting because of its restrictions on carbohydrate intake.

Simply put: when you want to build muscle, you want to eat large amounts of carbohydrate.

There are a couple reasons for this.

The first has to do with glycogen, which is a form of carbohydrate stored in the muscles and liver.

High-carb diets help maintain high levels of glycogen in the body, whichimproves workout performance. And the more strength and energy you have for your workouts, the better you can progressively overload your muscles, which leads to muscle growth.

Carbs’ insulin effects help with muscle building as well.

Insulin isn’t anabolic like other hormones such as testosterone, but it does have powerful anti-catabolic properties.

This means that insulin decreases the rate at which muscle proteins are broken down, which creates an internal environment more conducive to muscle growth.

And this is why several studies have shown that high-carb diets are superior to low-carb for building muscle and strength.

One was conducted by scientists at Ball State University, and it demonstrated that low muscle glycogen levels (which is inevitable with low-carb dieting) impairs post-workout cell signaling related to muscle growth.

Another was conducted by researchers at the University of North Carolina. They found that when athletes followed a low-carb diet, resting cortisol levels were higher and free testosterone levels were lower.

As cortisol is a catabolic hormone and testosterone an anabolic one, this is the exact opposite of what we want.

These studies help explain the findings of other research on low-carb dieting.

For example, a study conducted by researchers at the University of Rhode Island looked at how various levels of carbohydrate intake influenced exercise-induced muscle damage, strength recovery, and protein metabolism after a strenuous workout.

Subjects on a lower carb diet (about 226 grams per day) lost more strength, recovered slower, and showed lower levels of protein synthesis than subjects eating more carbs (about 353 grams per day).

Yet another example is a study, researchers at McMaster University compared high- and low-carb dieting with subjects doing daily leg workouts. They saw higher protein breakdown and lower protein synthesis rates in subjects on a low-carb diet, which resulted in less total muscle growth.

This is why I generally recommend a high-carb diet for gaining muscle and strength, and why carb cycling can be counterproductive for building muscle.

That said, just because it isn’t optimal doesn’t mean you shouldn’t do it.

As I mentioned earlier, you might find that your body is particularly sensitive to carbs and feels better when you reduce intake several days per week. You might also just like it more.

These are valid reasons to use carb cycling to build muscle.

How to Make a Carb Cycling Meal Plan

carb cycling meal plan

Now that we’ve put carb cycling in perspective and adjusted your expectations to reality, let’s talk about how to actually do it.

There are many different protocols, but I recommend you start with rotating between just two levels of carb intake:

  • A high-carb day
  • A low-carb day

You’ll often see regimens with a day of fewer than 30 grams of carbohydrate intake (no-carb days), but this makes compliance significantly harder in exchange for few practical benefits.

With that in place, let’s look at how to set everything up for both losing fat and building muscle.

How to Use Carb Cycling to Lose Fat

carb cycling sample diet

When you’re carb cycling to lose fat, you will have three low-carb days followed by one high-carb day.

Where you place your high-carb day doesn’t matter much because it moves around week to week.

For example, here’s how I would do it:

Monday: Low-carb day

Tuesday: Low-carb day

Wednesday: Low-carb day

Thursday: High-carb day

Friday: Low-carb day

Saturday: Low-carb day

Sunday: Low-carb day

Monday: High-carb day

And so forth.

Remember that when you’re carb cycling, you still have to plan and track your calories and macros if you want to guarantee results.

The starting point for determining where your food intake should be is yourtotal daily energy expenditure (TDEE). If you’re not sure what this is and how to calculate calorie deficits, read this article.

Here’s how it breaks down:

  • On your low-carb days, you should be in a 25% deficit.
  • On your high-carb days, you should be in a 10% deficit.

For example, my TDEE is currently about 3,000 calories, so my low-carb day’s calories would be around 2,250, and my high-carb days would be around 2,700.

Let’s now look at how those calories translate into macronutrients.

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  • Your protein intake should always remain at 1 gram per pound of body weight.
  • On your high-carb days, get 50% of your calories from carbs.
  • On your low-carb days, get 20% of your calories from carbs.
  • Get the rest of your calories from fat (“use” the calories left after calculating protein and carb intakes).

Here’s how a high-carb day would look for me:

190 grams of protein

335 grams of carbs

65 grams of fat

(For a total of about 2,700 calories.)

And my low-carb days would look like this:

190 grams of protein

110 grams of carbs

115 grams of fat

(For a total of about 2,300 calories.)

Once you have your numbers worked out, simply create a meal plan for both days and stick to them, alternating according to the 3:1 pattern.

It’s that simple.

How to Use Carb Cycling to Build Muscle or Maintain Your Body Composition

carb cycling bulking

If you want to use carb cycling to bulk or maintain your current body composition, you want to make a few changes to both your calories and macros.

First, I recommend a 3:2 low/high-carb ratio (every five-day cycle consists of three low-carb days and two high-carb days).

The low-carb days help reduce water retention, making you look leaner, and the additional high-carb day helps with your training and muscle gain.

Your low- and high-carb days don’t have to be lined up in a row. Some people like to follow three low-carb days with two high-carb days, and others like to stagger them based on how they’re feeling in the gym, doing let’s say one high-carb day, one low-carb day, one high-carb day, and two low-carb days.

I would try to schedule most of my high-carb days to fall on days that I’m lifting weights and most of my low-carb days on days I’m not (although some of your training days will inevitably be on low-carb days).

In terms of working out your calories, here’s how to do it:

  • If you’re bulking, set your daily intake to 110% of your TDEE.

Read this article to learn more about proper bulking.

  • If you’re maintaining, set your daily intake to 100% of your TDEE.

And for the macros:

  • Your protein intake should always remain at 1 gram per pound of body weight.
  • On your high-carb days, get 50% of your calories from carbs.
  • On your low-carb days, get 25% of your calories from carbs.
  • Get the rest of your calories from fat.

So, using myself as an example, here’s a high-carb day for maintenance:

190 grams of protein

375 grams of carbs

80 grams of fat

(A total of about 3,000 calories.)

And a low-carb day:

190 grams of protein

190 grams of carbs

165 grams of fat

Again, once you have your numbers, all you have to do is create a meal planand stick to it.

The Bottom Line on Carb Cycling

carb cycling calculator

In many ways, carb cycling is like intermittent fasting.

Both are valid, workable dietary strategies that have been seized on and sensationalized by fitness “gurus” and marketers.

Unfortunately, neither can deliver on many of the promises made, but that doesn’t mean they have no use. They just need to be undertaken with sober expectations, and I hope this article helps in that regard.

So, if you know that your body is particularly sensitive to carbs or if you just want to see how it will respond to carb cycling, give it ago. And if you do and don’t like how you feel or don’t see any benefits over traditional dieting, ditch it.

Remember that in many ways, the best diet is the one you can stick to.

In many ways, the best diet is the one you can stick to.

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For me, that’s a flexible diet that entails eating every few hours but saving large portion of my daily calories for later at night, after I’m done working.

For you, it might be carb cycling.

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