CBL - The Dream of Building Muscle Without Gaining Fat?

Dear BLOG readers, dear PEAK customers, CBL stands for Carb-Backloading, a dietary approach still relatively unknown in Germany that was developed by a man named John Kiefer. He is revolutionizing the entire field of nutrition by promising lean muscle gain to those who follow his dietary system.

Since John Kiefer’s CBL has so far only been available as an English e-book, his idea has not yet gained widespread popularity in Germany. Fortunately, the authors of the website www.aesirsports.de have taken the trouble to translate the most important facts and make them available on their homepage, along with their own insights.

Today, as I’ve done before with the anabolic diet and the metabolic diet, I’d like to take a critical look at CBL and, over the course of the next three blog posts, provide you with a neutral, well-founded evaluation of this dietary approach from my perspective.

Although John Kiefer’s e-book was made available to me, I will base my evaluation exclusively on the German translation, since the “average” German reader is more likely to rely on this source.

Even though there are a few points worth criticizing, CBL does contain several interesting approaches worth exploring.

I hope you enjoy my analysis

CBL—The Dream of Fat-Free Muscle Gain?

CBL – A Brief Overview

Before we take a look behind the scenes of CBL, I’d like to give a very brief overview of what CBL is actually about and how it works:

The CBL Commandments

• Don’t eat breakfast
• Eat a “ketogenic” diet during the day (under 30g of carbs), with moderate fat and plenty of protein
• Work out between 4:00 p.m. and 6:00 p.m.
• Immediately after your workout, start with a shake containing short-chain carbohydrates and protein hydrolysates
• After that, until bedtime, consume a high amount of carbohydrates as well as moderate amounts of protein and, if you like, fat

Conclusion

CBL explained briefly and concisely in 5 bullet points—but it’s not quite that simple

Who is CBL suitable for?

This question is crucial—and it’s important to address it before diving into the theory behind CBL.

Can anyone benefit from CBL, or is the group of people who can expect to build lean muscle very limited?

To get this out of the way:

The founder himself apparently excludes certain groups of people from CBL for specific reasons. You’ll find out now what those reasons are, why they exist, and how to interpret them:

Hardgainers

According to Kiefer, CBL is a problem for so-called hardgainers if they struggle to meet their daily calorie needs. Anyone who is confident they can still enjoy evening feasts of carbohydrates to their heart’s content should follow the CBL path.

For a person weighing 70 kg, the system specifies a daily intake of approximately 546 g in one of the two formulas used to determine carbohydrate requirements—an amount that is consumed exclusively after the evening workout.

Criticism

Consuming such high amounts of carbohydrates, spread out over just a few hours, will likely result in a vicious cycle of bloating, abdominal cramps, and other digestive issues for hardgainers who may be struggling with impaired carbohydrate absorption.  The issue of feeling full too soon is certainly a problem that can arise, even though the CBL diet is generally low in fiber.

Conclusion

CBL rightly excludes the majority of hardgainers

Pregnant women

According to Kiefer, CBL and pregnancy don’t mix, but why not?

I’ve already provided a possible answer in one of my blog posts on the topic of pregnancy and exercise:

Quote:

The older the fetus, the more the expectant mother’s metabolism increases, demanding glucose. This leads to an increased need for glucose, with the result that blood sugar levels in mothers tend to be lower than in non-pregnant women. Increased glucose availability is influenced by the hormones cortisol, glucagon, and insulin. Cortisol is the hormone that reduces cellular glucose uptake as well as insulin sensitivity. During pregnancy, insulin sensitivity is only about 80%. High demand leads to increased glucose production, but this glucose has a harder time entering the cells… we see similar conditions in people with diabetes.

Criticism

Insulin resistance is more pronounced in pregnant women because there must always be enough glucose in the blood available for the unborn child. High amounts of ingested carbohydrates—such as those consumed in the evening with CBL—therefore remain in the blood longer. To a certain extent, this desensitization also affects muscle cells following an intensive workout (as intense as is possible and reasonable).  – The CBL effect is thus eliminated or significantly reduced
 

During the day, the countless hours spent without any carbohydrates can also become a problem. Although hypoglycemic episodes typically occur less frequently during pregnancy, stress hormone levels will rise dramatically and may also affect the fetus. – CBL is even potentially dangerous in this context

Conclusion

CBL and pregnancy are mutually exclusive

Women

By only considering the use of CBL for women to a limited extent, Mr. Kiefer’s methodology largely overlooks a very large target group. It’s a shame, but probably necessary, since there are significant differences in metabolism between the sexes. There is also already some in-depth information on this topic in my blog post about pregnancy and exercise:

Quote:

Unlike men, women do not experience a drop in blood sugar levels at the end of exercise. This can be attributed to the fact that catecholamine levels are significantly higher in women than in men.

The higher triglyceride levels typically found in women—along with their generally higher body fat percentage—enable them to utilize free fatty acids as an energy source more readily, thereby conserving glucose.

Criticism

Compared to men, women metabolize fatty acids for a much longer period and turn to carbohydrates much later. Nevertheless, processes that are so important for functionality—such as GLUT-4 activation and GLUT-4 upregulation following strength training—also occur in women (albeit not to the same extent as in men).

Women should be able to handle the low-carbohydrate phase during the day quite well. In principle, one would simply need to develop a CBL adapted to women’s metabolism and would thus have gained a new target group. The existing weight-based guidelines regarding carbohydrate intake must in any case be considered inapplicable to women, since women expend less energy for the same amount of muscular work and their glycogen storage capacity is entirely different. Even the method of calculating carbohydrate requirements based on glucose and water depletion will have limited applicability for women. Here, additional consideration would need to be given to factors such as the menstrual cycle and several others.

Conclusion

To date, CBL has essentially been reserved for men and very adventurous women who know themselves well enough to determine their required carbohydrate intake.

Endurance Athletes

Since there are still no proper guidelines for women in general, female endurance athletes will find it even more difficult to successfully apply CBL. Compounding the difficulty for endurance athletes as a whole is the fact that the author implies that, in terms of training intensity, they do not ensure sufficient GLUT-4 activation and thus do not achieve a sufficient increase in muscle insulin sensitivity after training.

Criticism 1 – Insulin Sensitivity and Endurance Sports

That is not entirely accurate. It is also known that endurance exercise (when performed regularly) is capable of altering gene and protein expression in skeletal muscle in a way that leads to an increase in the insulin sensitivity of skeletal muscles. It has been demonstrated that, specifically for the GLUT-4 transporter, this results in an increase in messenger RNA and enhanced protein expression. Furthermore, an increase in PI3-kinase activity allows the insulin signal to be transmitted more effectively from the receptor after exercise. These changes are caused by the development of cellular and oxidative stress and, consequently, the formation of ROS (reactive oxygen species). They trigger the activation of AMPK (AMP-activated protein kinase), a kind of metabolic master switch.

Endurance sports, in particular, also activate MAPK p38, the mitogen-activated protein kinase signaling cascade, which further enhances the effects of AMPK.

Criticism 2 – Endurance Athletes and Their Training

One should not assume that endurance athletes engage exclusively in endurance-oriented training. Just as endurance training can be an additional component for strength athletes, strength training also constitutes a more or less significant part of the total training volume for endurance athletes. Kiefer himself excludes anaerobic sessions—such as intervals or HIIT—from classic aerobic endurance training. These exercises also feature in all training plans for endurance athletes, ranging from moderate to high volume depending on their training level and proximity to competition.

Conclusion

While CBL represents a good dietary approach for strength athletes, the reasons for exclusion mentioned above are not relevant for endurance athletes.

What’s left?

What remains is the rest of the male population who, due to their metabolic type, have no trouble building muscle but struggle to keep body fat in check. We’re talking about mesomorph and endomorph body types.

Although it’s a real shame that CBL seems to work properly only for such a limited group of athletes, it would certainly be a relief for those affected to be able to build muscle without a significant increase in fat (or even while simultaneously losing fat).

Summary

CBL is primarily reserved for men with endomorphic and mesomorphic body types. The system was apparently designed mainly for them, although with some thought and redesign, women and endurance athletes can also be incorporated.

Now it’s time to examine what CBL is truly capable of….

CBL – A Look Behind the Scenes

GLUT-4 Transporters

The theory behind CBL relies largely on an increase in the number and activity of GLUT-4 transporters in muscle cells, while maintaining low levels in fat cells. The goal is the controlled distribution of the large amount of carbohydrates consumed after the evening workout. The theory itself is truly fascinating.

What Are GLUT-4 Transporters?

GLUT-4 transporters are molecules found in fat and muscle cells that regulate intracellular glucose transport. They are primarily produced and activated in response to insulin. Through an insulin response, the transport of glucose into the cells can be increased by a factor of 10 to 40.  The purpose of GLUT-4 transporters is to ensure a demand-driven supply of glucose.

The presence of insulin therefore increases the number of GLUT-4 transporters. In addition, mechanical stimuli triggered by both strength and endurance sports lead to an increased number and higher activity of GLUT-4 transporters.

The combination of physical activity and the intake of short-chain carbohydrates leads to a maximization of GLUT-4 transporters in muscle cells. The GLUT-4 capacity and GLUT-4 activity of fat cells, on the other hand, remain unchanged.

So far, so good:

Combine training with short-chain carbohydrates!!

BUT

Is this new? - NO – this is exactly what has been preached in the bodybuilding scene for many years

Conclusion

Anyone who does strength training will experience improved insulin sensitivity along with an increase in GLUT-4 expression and enhanced GLUT-4 activity. If short-chain carbohydrates are consumed in conjunction with this, it can lead to a significantly increased uptake of glucose into the trained muscle cells. At the same time, particularly in fat cells, both insulin sensitivity and GLUT-4 levels remain unchanged AS LONG AS CARBOHYDRATES ARE NOT CONSUMED IN EXCESS EVEN IN THIS SITUATION!

Summary

So far, we haven’t learned much about CBL itself, except that it is unfortunately not suitable—or only partially suitable—for a significant group of people. To what extent Kiefer has already expanded CBL to other target groups is unknown to me at the time of writing this blog post. Unfortunately, the German-language documentation limits its use to only a small portion of the population.

The concept itself sounds very revolutionary, especially given the structure of the day and the distribution of nutrients. While carbohydrate intake after exercise is certainly nothing new—due to the activation of GLUT-4 transporters and improved insulin sensitivity—many of you are likely reading the recommendation to eat additional carbohydrates in the evening for the very first time today. This makes it all the more interesting for you to also explore Parts 2 and 3 of my blog and join me in delving deeper into CBL.

Until then, I send my best wishes

Best regards

Yours,

Holger Gugg

www.body-coaches.de