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Build Muscle and Burn Fat – Body Recomposition Facts

The holy grail of fitness is to build muscle and burn fat simultaneously. But is body recomposition possible, or is it another fitness myth? This is an issue that has perplexed man for as long as time itself. But not anymore: Fitness Savvy is here to tell you that it is entirely possible, and have the evidence to prove it.

We’re going to jump right in and tell you the answer. And then you can read on to find out how and why it’s possible.

My name is Robin, and I came up with the idea for Fitness Savvy in January 2017. My aim is to debunk fitness myths, and help people find in-depth scientifically backed articles. The image for this blog is my DEXA body scan taken at Bodyscan UK. The first image (on the left) was taken on 6th March 2017, and the second 3 months later on 5th June. While writing this article, I conducted a lot of research which I then used to design my body recomposition workout plan. I gained 8.4lb of muscle and lost 6.2lb of fat. The amount of muscle gained is consistent with the 2 primary pieces of evidence I came across while researching this article. Therefore, we conclude that it is 100% possible to build a significant amount of muscle while burning fat.

Not only did I recomp, but my arms grew massively – as discussed in my article about building big arms. But the kicker is that I didn’t train my arms! No direct isolation work whatsoever.

So let’s see how it’s done:

The Law of Thermodynamics

Once upon a time, there was a man. A fantastic and intelligent man. A man of science and wisdom. His name was Isaac Newton. You’ll be greatly surprised to discover that he had absolutely nothing to do with the law of thermodynamics, and so we shall mention him no more within this article.

All you really need to know in regards to thermodynamics is that energy can neither be created nor destroyed – it simply changes forms. If you wish to find out more on this subject, hunt down an enthusiastic science teacher with nothing better to do than entertain the inquisitive mind of potential stalkers!

The Energy Balance Equation

Nevertheless, the laws of thermodynamics lead us on to the energy balance equation – which is what we are most interested in here. As described on the website, this equation – in its simplest form is:

Energy in = Energy out + Change in Body Stores

Now, as most will already know, if you eat lots of food and don’t exercise you will likely put on weight. This is because you are consuming a shed load of calories and that energy is then stored. The energy is stored in cells – most typically fat and muscle cells. In contrast, if you are eating less, therefore not feeding your body the energy it requires, cell oxidation will occur, which is where your body breaks down fat and muscle cells to release the energy stored within them.

So energy in is simply the calories you are consuming, right? Not exactly; different nutrients digest in different ways, and all behave differently – not simply depending on the nutrient in question, but also your genetics, activity level and other foods you may be consuming. An example is that foods with a high glycaemic index will stimulate insulin release, which can result in energy being stored as fat, rather than being readily used by the body. Once this energy is stored, it won’t be broken down and used as easily as readily available energy sources – such as when you eat again. Another example is that fibre tends to bind tiny amounts of protein and fat in the stomach, which is then disposed from the body without being digested. So if the meal was also high in fibre, the calories consumed may not be as high as you think.

It is recognised that to grow in size (increase mass), one requires a positive energy balance, and for one to shrink in size (decrease mass), one requires a negative energy balance. Therefore, one would assume a positive energy balance necessary to grow new muscle, and a negative energy balance to burn fat. And this is the fundamental argument for those who state that it is impossible to build muscle and burn fat at the same time. They argue that the body does not simply change from one to the other.

Maintaining a Positive Nitrogen Balance

When looking at body recomposition, the fear of muscle break down deters many from even trying. It is natural to perceive excessive calories as being fundamental for muscle protein synthesis – especially in an age where the bulking and cutting cycle are regularly hailed a necessity.

However, a positive nitrogen balance is the primary objective. One study looked at the effect of a hypocaloric (restricted calorie) diet, and increased protein intake combined with resistance training on lean mass gains and fat mass loss in overweight police officers.1 The 12-week study compared three groups:

  1. Group 1 – placed on a hypocaloric diet (80% of predicted caloric needs). No resistance training, and no protein supplementation.
  2. Group 2 – placed on the same hypocaloric diet. Engaged in resistance exercise, and consumed 1.5g per kilogram per day of casein protein hydrolysate.
  3. Group 3 – placed on the same hypocaloric diet. Engaged in resistance exercise, and consumed 1.5g per kilogram per day of whey protein hydrolysate.

The results showed a mean fat loss of 2.5kg for group one, 7.0kg for group 2, and 4.2kg for group 3. Lean mass gains were negligible for group 1, versus gains of 4kg in group 2 (casein group) and 2kg in group 3 (whey group). Mean increase in strength for chest, shoulder and legs was 59 +/- 9% for casein and 29 +/- 9% for whey – a significant group difference.

This great difference in body composition and strength was attributed to improved nitrogen retention and overall anticatabolic effects caused by the peptide components of the casein hydrolysate.

This is one of many studies which support the argument that losing fat and gaining muscle simultaneously is possible. Another study worth considering looked into whether muscle hypertrophy was possible with large-scale weight loss.2 Biopsy samples were taken from the vastus lateralis muscle at baseline and after 90 days of weight training. The cross-sectional area of slow twitch and fast twitch fibre significantly increased in the weight trained subjects.

Calorie Restriction and its Effects on Glucose Uptake

Glucose is a simple sugar which circulates the body in the blood.

If fat cells can uptake glucose (which can later oxidise to release energy), what makes muscle cell uptake more preferential? The primary reason is this: Muscle cells lack glucose-6-phosphatase which is required for glucose to be passed into the blood. Therefore, the glycogen muscle cells store is available exclusively for internal use and is not shared with other cells.3

If contracting muscles require glucose,4 and one is looking to reduce fat and increase lean body mass, then one must ensure that there is enough energy to supply the contracting muscles. By encouraging glucose uptake by muscle cells, two birds are killed with one stone: firstly, muscles have the energy required for the next workout without oxidation of muscle cells, and excess glucose is stored within the muscle as opposed to fat cells. A study found calorie restriction increases glucose uptake by skeletal muscle cells,5 ergo, restricting calories = greater uptake of glucose by muscle which is exactly what we want.

However, those in a caloric deficit tend to consume lower levels of BCAA (branch-chained amino acids), and therefore, to ensure necessary levels of BCAA continue circulating the body (which is essential for normal everyday function), muscle cells will break down in order to release them. By supplementing with BCAAs during times of calorie restriction, a comfortable level will remain to limit muscle catabolism, and on training days whereby calories, nutrients and BCAAs are consumed to a normal or minimally excessive level, the body will be anabolic, therefore, muscle protein synthesis will be operating in full flow.

Here you can read a detailed article on BCAAs.

Popular BCAAs – Compare Prices 

How Fast Can I Recomp?

The speed at which one can build muscle and burn fat will, as usual, vary. Two extremes are set out below:

  1. You are an individual who has never engaged in resistance training before. You are a high body-fat percentage (25%+ for men, 35%+ for women). You are highly likely (providing strict diet and a proper training programme) to recomp quickly. Bodyscan UK wrote a blog regarding one of their clients, which showed a reduction in body fat of 11.5kg, and an increase in muscle mass of 6.4kg. This was achieved on a calorie deficit, with no protein supplementation and – challenging all the preconceptions that testosterone is required to build muscle – this client was female! This was achieved in less than 5 months!
  2. You are an individual who is on the leaner side, and you have engaged regularly in resistance training. You are likely to find it more challenging, as your body has already acclimatised to the shock growth which occurs when first introducing your muscles to heavy weights. Your muscle gaining potential is lower, and because you are already carrying less body fat, your body will want to hold onto what it has and will be more likely to store more fat or break down muscle tissue for energy.

When looking to reduce weight and increase muscle size or simply retain lean body mass, it is advisable not to restrict calories too much. In the example above, the woman only restricted calories by 500 per day on average and lost a total of 0.32kg (.7lb) of weight per week. Reducing weight at a slower pace has been shown to be more desirable.6

Recomp Diet Requirements

Now that we’ve established that body recomposition is possible, let’s look at what we’ll need to be eating, and when.

Let’s start off our section on diet by addressing the elephant in the room – protein intake. There is much confusion over the level of protein required to build or maintain muscle. The level depends on many factors such as lean body mass, whether in a caloric surplus or deficit, how often you train, your sex, and fitness goal. Conflicting arguments rage on – and if you are anything like I used to be – you will keep changing your plan based on the most recent articles. But that all ends here.

We have taken many studies and built a calculator to provide something far more sensible. It accounts for lean body mass, whether you are in a caloric deficit, and the activity you are engaging in, as well as comparing your habitual protein intake – if known.

Check out our Protein Calculator, which includes references to scientific research we used to build the calculations.

The next thing we will address is the need to cycle our diet. This means we will eat more on workout days and less on rest days. The idea of cycling calories has been looked into for many reasons: firstly, it is anecdotally reported to help prolong periods of weight loss by delaying the plateau. Other studies have shown calorie cycling can actually prolong life.7

For our Body Recomposition plan we recommend four days of resistance training and three rest days. The workout plan is covered in detail here.

Using a BMR calculator we can establish our basic caloric needs. Once we know our BMR, we multiply by 1.5 to establish the calories required to maintain our weight. It will also be the number we eat on workout days.

A lower level calorie limit must be set to ensure we reduce the potential for muscle cells being used for energy. For this reason, we will consume the level shown as our BMR on rest days at an absolute minimum.

The net total is a weekly caloric deficit in this example of around 17%. We suggest restricting calories further if your primary aim is fat loss. What we mean here, is that two people can both be 25% body fat. However, one might already have a large amount of muscle mass. Think bulky rugby players who are not toned, but you can tell they have a serious amount of muscle. Then there is the “skinny-fat” guy. This person is also 25% body fat. But this is because he has little muscle mass. His aim is to build as much muscle as possible without putting on any more fat. This individual could look to consume calories at just below maintenance.

Macro Breakdown

On workout days, we will consume a slightly larger proportion of carbs, and on rest days we will restrict carbs for a few reasons:

  1. Our caloric needs on rest days are lower.
  2. Carbs spike insulin which can result in higher fat storage, so limiting carbs on rest days will limit the scope for this.
  3. Ideally, we should consume carbs after a workout to prompt a beneficial insulin response, as discussed earlier.
  4. Lower carbs will lead to our body resorting to fat as its primary energy source.

Your fat and carb macros will partly depend on your body type. For example, the ectomorph or mesomorph will be able to consume more carbs, generally speaking. The endomorph will look to restrict carbs much more strictly. Find out more about body types.

For this example, we are going to use the endomorph body type. We have already produced an article on endomorph diets here. The macro breakdown calculated in this article will be our starting point.

As usual, we firstly calculate our protein requirements. For this example, we are going to assume the following:

Sex:              Male

Weight:       145lb

Body Fat:    25%

Fat will make up around 50% of Macros on both training and rest days.

As calculated using the unique Fitness Savvy Protein Calculator, 124g of protein will be consumed per day.

The rest of the calories on both days will be made up of carbs. Below is a table of our total calories on each day, and how they are broken down.

The calculator below is the basis for another awesome Fitness Savvy tool we are creating. Once it is complete, we will add the recomp calculator link to this article. It is currently hiding in an excel file at the moment and needs to be converted.

Get Your 8 Hours!

You may have heard the expression: “Eat, lift, sleep, repeat”. This refers to the three pillars of successful muscle building:

  • Train hard
  • Eat well
  • Get some decent sleep

Sleep regulates important hormones dedicated to keeping your body and mind fit and healthy. Damaged cells are broken down and repaired during sleep, too. You will maximise your body’s ability to build muscle if you sleep for 7-9 hours. Sleep deprivation affects hormones as follows:

  • Growth hormone – as its name suggests, promotes cell growth. The levels of this hormone decrease from lack of sleep.
  • IGF-I – short for Insulin-like growth factor – induces protein synthesis and blocks muscle atrophy. As with the growth hormone, this is suppressed, also.
  • Prolactin – a hormone involved in hundreds of biological processes – follows in the same footsteps as both growth hormone and IGF-I.
  • Leptin – a hormone which inhibits hunger is also restricted.

Check out our detailed, research-backed article on the importance of sleep if you would like to know more.

Compare Prices On Sleep Aids

Consume 25-40g of Casein Protein Just Before Bed

Before you settle down for your eight hours of blissful sleep, be sure to ingest a good portion of protein. People often confuse the facts and believe decent sleep is important for building muscle. However, it is more likely to be an action taken to prevent muscle catabolism (the breaking down of muscle cells to release energy and amino acids while the body is fasting). Protein synthesis is actually pretty low during sleep – even when 20g is consumed just before bed, as discussed by Jorn Trommelen and Luc J. C. van Loon in their paper: Pre-Sleep Protein Ingestion to Improve the Skeletal Muscle Adaptive Response to Exercise Training.8

While acknowledging the fact that some studies have shown whey protein as superior at stimulating muscle protein synthesis9, they draw attention to the fact that these studies were only assessing up to 6 hours, and highlight that it remains to be established if whey protein is superior when ingested prior to sleep, with muscle protein synthesis rates being assessed over a more prolonged overnight period of 7.5 hours. Further studies have suggested that even post workout, casein protein is just as good as whey.

Given the effectiveness of casein protein in both the above-mentioned study and the one concerning body recomposition in overweight police officers, we are happy to recommend casein protein as the most appropriate supplement to use while recomping. This is also supported by the fact that casein is a slowly digestible protein source, allowing a more moderate but prolonged rise in plasma amino acid concentrations during periods of caloric deficit and sleep.

While I was training, I tried a couple of types of casein. My personal favourite was the chocolate casein from Bulk Powders. It has 108 calories and 27 grams of protein per serving. We also have a huge selection of casein proteins to compare prices on from many of the top nutrition brands including Optimum Nutrition, Myprotein, The Protein Works, Grenade and many many more.

Casein Protein – Compare Prices on Popular Branded Products

Training for Body Recomposition

The training programme we have designed for body recomposition comprises 4 resistance sessions using an upper and lower body split, as follows:

So what about cardio? This is covered in the aforementioned article, but we will cover it very briefly here: As with everything in the fitness world, there is much conflicting information out there to confuse us all! In regards to cardio, I am not a huge fan. Walking every day for half an hour is great, and if you want to throw in a couple of half-hour cardio sessions because you enjoy it – knock yourself out. However, given that some studies suggest negative hormonal responses which could be detrimental to muscle gain, we advise steering clear if you’re “skinny fat”. However, if you already have a naturally decent level of muscle and want to speed the process up, or eat more, throw in some HIIT cardio sessions.

BUT REMEMBER… the most important thing is to ENJOY your workouts! If you don’t enjoy what you’re doing, you might not continue long enough to reap any rewards – and that’s the worst possible scenario. I read a study by Foster et al., 2015, comparing HIIT (High Intensity Interval Training) with Steady State Training on Aerobic and Anaerobic Capacity.10 The biggest point they make in their concluding remarks is that HIIT was found to be less enjoyable and that:

“Perhaps variety in the type of exercise is as important as the type of exercise per se, particularly considering that the health benefits of exercise have to be viewed in the context of the likelihood that exercise is continued for several years, not just the weeks of a controlled study. Perhaps, in our quest to find the ‘perfect exercise’ we have missed the more important issue of how to make exercise enjoyable enough to be continued long-term.”


So here it all is in a nutshell:

1: Restrict your calories on non-training days, aiming for a level calculated as your BMR. Supplement with BCAAs to ensure enough branched-chain amino acids are present in the blood to prevent muscle being broken down to free some up. You have limited the ability to break down muscle for fuel and primed your body for improved insulin-induced glucose uptake, as previously discussed.

2: Consume around 40g of Casein protein just before you go to sleep. Aim for 8 hours sleep. This will limit muscle atrophy, and in some cases (provided enough protein is taken prior to sleep) promote muscle growth.

3: Engage in resistance exercise on training days, concentrating primarily on heavy, compound lifts – as covered in our recomp workout article. Remember – a training day is only one where you lift weights for at least 40-60 minutes. The combination of restricted calories and exercise contribute to greater glucose uptake into muscle cells, priming your body for optimum recomposition.

4: Eat at calorie maintenance (or a minor surplus – of 100 calories or so) on training days to fuel protein synthesis and replenish glycogen. Consume the bulk of your calories shortly after your workout (preferably within an hour), as many studies have shown meal timing to be an important factor for protein synthesis.11

Our Final Words

So there you have it: build muscle and burn fat at the same time – because it is entirely possible. We have covered your diet plan, provided you with the most comprehensive protein calculator around, drawn up an upper/lower body split resistance training programme, and filed this report in our NO-BRO ZONE as scientific FACT.

If looking to get your hands on some of the supplements mentioned – check out our awesome price comparison pages. We have brought together a massive range of popular supplements from a ton of retailers so you can be sure you get the best prices and deals. You can filter by product, serving size, brand, dietary requirements, and even BCAA ratio then find who sells the best supplements at the best prices.


  1. Demling RH, DeSanti L. Effect of a hypocaloric diet, increased protein intake and resistance training on lean mass gains and fat mass loss in overweight police officers. Ann Nutr Metab. 2000;44(1):21-9.
  2. Donnelly JE, Sharp T, Houmard J, Carlson MG, Hill JO, Whatley JE, Israel RG. Muscle hypertrophy with large-scale weight loss and resistance training. Am J Clin Nutr. 1993 Oct;58(4):561-5.
  3. Wikipedia – Glycogen
  4. Richter EA, Hargreaves M. Exercise, GLUT4, and skeletal muscle glucose uptake. Physiol Rev. 2013 Jul;93(3):993-1017.
  5. Wang H, Arias EB, Cartee GD. Calorie restriction leads to greater Akt2 activity and glucose uptake by insulin-stimulated skeletal muscle from old rats. Am J Physiol Regul Integr Comp Physiol. 2016 Mar 1;310(5):R449-58.
  6. Garthe I, Raastad T, Refsnes PE, Koivisto A, Sundgot-Borgen J. Effect of two different weight-loss rates on body composition and strength and power-related performance in elite athletes. Int J Sport Nutr Exerc Metab. 2011 Apr;21(2):97-104.
  7. Brandhorst S et al. A Periodic Diet that Mimics Fasting Promotes Multi-System Regeneration, Enhanced Cognitive Performance, and Healthspan. Cell Metab. 2015 Jul 7;22(1):86-99.
  8. Trommelen J, van Loon LJ. Pre-Sleep Protein Ingestion to Improve the Skeletal Muscle Adaptive Response to Exercise Training. Nutrients. 2016 Nov 28;8(12). pii: E763.
  9. Pennings B, Boirie Y, Senden JM, Gijsen AP, Kuipers H, van Loon LJ. Whey protein stimulates postprandial muscle protein accretion more effectively than do casein and casein hydrolysate in older men. Am J Clin Nutr. 2011 May;93(5):997-1005.
  10. Foster et al. The Effects of High-Intensity Interval Training vs Steady State Training on Aerobic and Anaerobic Capacity. J Sports Sci Med. 2015 Dec; 14(4): 747–755.
  11. Biolo G1, Tipton KD, Klein S, Wolfe RR. An abundant supply of amino acids enhances the metabolic effect of exercise on muscle protein. Am J Physiol. 1997 Jul;273(1 Pt 1):E122-9.


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Rob is the founder and CEO of Fitness Savvy. He's online most of the time and happy to answer questions regarding nutrition, fitness and the site in general.

1 Comment
  1. Science and fact really enjoyed reading this article, I will be keep posted.

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