How can you gain muscle while losing fat & more [interview]

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After my 3 recent interviews by Italian groups, next up is a short interview by the Turkish website Agir Saglam. The topics are:
  1. The Bayesian Bodybuilding philosophy
  2. The mechanism of how you can build muscle and lose fat at the same time
  3. Intermittent fasting


You can read the full interview in Turkish here. Below I’ve posted the English original.



First off, what is Bayesian Bodybuilding and how does your Bayesian approach make a difference?
Bayesian Bodybuilding is based on the statistical and logical reasoning principles that were first invented by Thomas Bayes. Basically, this just means it’s a rational approach to bodybuilding. That alone makes it very different from the traditional bro culture that is mostly based on feelings: the pump, the burn, soreness, feeling a muscle, etc.


The Bayesian method is heavily influenced by science, but it takes all forms of data and evidence into account. Furthermore, Bayesian principles specify how to form rational beliefs based on the available information. So where science only concerns itself with the truth about the state of nature, Bayesian reasoning will actually make the step beyond science to form beliefs about the most reasonable practical implementation.


You showed us adding muscle mass in a caloric deficit is achievable. You even state it is not only possible but also should be expected in your article. Briefly, how does this mechanism work?


Indeed, body recomposition is greatly underestimated. In today’s evidence-based fitness culture of ‘nothing matters, nothing works’ most people’s results are so poor that they don’t even believe it’s possible to build muscle mass while losing fat at the same time, yet it occurs literally in dozens if not hundreds of studies (see my article about body recomposition for several references even in advanced lifters). Unless you’re close to your genetic muscular potential or you are close to contest shape, you should be gaining some muscle mass on a cut if your program is optimized.


Now, this has led some people to believe that when I say ‘optimized program’ I have a magic trick up my sleeve that I use with my clients. That is not the case. Many of my clients have years of training experience, they get their protein in, watch their macros and train hard, so all the fundamentals are already there. What I do is tweaking. I optimize everything. Their macros, nutrient timing, exercise order, exercise selection, training volume, the implementation of autoregulation, periodization, sleep and stress levels, their food choices, etc. So successful body recomposition depends on doing everything right. There is no 1 magic trick.


As for the mechanism, first, you have to realize that fat mass (adipose tissue) and muscle mass are distinct compartment in the body. At any time, your body is breaking down and building fat as well as muscle mass. So you are looking at net balances over time. There is no reason why your body can’t modify both lean and fat tissues at the same time. It does so all the time. Denying this would be like saying you can’t heal a fractured bone unless you’re in energy surplus. Or a liver transplant patient will never accept the liver unless the patient is in energy surplus. It’s silly.


It does need substrate to build muscle mass of course. You need building blocks to build a house. Let’s look at what exactly the body needs. Heymsfield et al. (1982) were kind enough to cut up some dead people for us, so I’ve aggregated their results from the healthy control group in the following image. This is the composition of human muscle tissue.


Muscle tissue composition


So what do we need to build muscle mass?

  1. Lots of water (H2O). You can drink plenty of that during a cut, so no problems there.
  2. Several kinds of protein. Again you can eat enough protein on a cut, so no problems here either. For the DNA and RNA we also need nitrogen and phosphate, but those can be derived from dietary protein.
  3. Glycogen and triglycerides. This basically just comes down to energy, because glucose and fat are non-essential nutrients that can be created by the body itself. We need a lot more energy too, because the protein synthesis for the muscle building process is an energy costly process itself.


In short, we need protein, water and energy. Where do we get the energy? Easy. Your body has plenty of that. Let’s take myself in average photoshoot condition at about 87 kg, 6% body fat. People think of this conditioning as ‘having almost no fat’, but the truth is, there’s still plenty of fat even then: 5.2 kg to be exact. If we convert that to metabolizable energy based on the density figures I gave in my article about energy balance myths, the body still has over 49000 calories right there for the taking. That’s plenty to build pounds and pounds of muscle without even taking into account you’re still consuming energy in your diet as well.


So as long as your body has sufficient stimulus to build muscle mass, which it has if your training program is optimized, it has both the means and the will to build muscle mass while simultaneously losing fat. There you go, muscle growth during a cut.


What are your thoughts on using intermittent fasting and macronutrient timing methods for body recomposition?

Nutrient timing is a very extensive topic, so I’ll focus specifically on intermittent fasting (IF). IF used to be a major hype after the rise and fall of Martin Berkhan and it has definite merits. Consistent breakfast skipping – which is how most people think of IF even though it’s just 1 implementation of it – is particularly well suited for certain personality types. This is seen in research as well as my client base.


However, it is not the magic best-method-for-everyone fat loss tool that the cult followers make it out to be.

  • Extending the fast for too long has been shown to impair anabolic signaling in muscle.
  • Fasting across midday has been shown to impair cognitive functioning in some research.
  • Ironically, intermittent fasting zealots tend to name improved insulin sensitivity as a major benefit. This is only true in uncontrolled settings where fasting causes fat loss, which then improves insulin sensitivity. The overall literature on fasting and insulin sensitivity or blood sugar levels is not favorable at all.
In short, IF is a useful tool to have. It is right for certain people in certain situations, but it should not be your one-size-fits-all fat loss method.

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About the author

Menno Henselmans

Formerly a business consultant, I've traded my company car to follow my passion in strength training. I'm now an online physique coach, scientist and international public speaker with the mission to help serious trainees master their physique.

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