Building muscle and losing fat at the same time: is it possible? Six measurable levers
The essentials at a glance
Yes, both at the same time are possible. In sports science, the process is called body recomposition, meaning muscle gain while losing fat at the same time. It is most likely to work for beginners and people with overweight. It has also been documented in people who train with weights, but it proceeds slowly there (Barakat et al., 2020).
The catch is not whether it works, but that you will barely notice it. The scale changes little because two processes are running in opposite directions. Anyone who tracks only their weight mistakes progress for stagnation and gives up. That is why this article turns each of the six levers into a value you can check.
Chapters 2 and 3 provide the research findings and four numbers. Chapter 4 explains who can realistically achieve it. The levers are covered in chapters 5, 7, and 9, with an overview in chapter 8. Chapter 12 outlines the limits. You will not find a training or nutrition plan here.
What to expect in this article
1. Can you do both at the same time, or do you have to choose?
2. What the research says about recomposition
3. Four numbers that set the framework
4. Who can realistically achieve it
5. Levers 1 and 2: protein and amino acid status
6. Four persistent beliefs
7. Levers 3 and 4: sleep and cortisol
8. The six levers made measurable
9. Levers 5 and 6: strength-training days and genetics
10. Who can benefit from a test
11. Which tests measure what
12. Limits: what numbers cannot tell you
13. What you can do differently tomorrow
Frequently asked questions
Sources
Can you do both at the same time, or do you have to choose?
The rule passed down in every gym is: first build mass, then define. Muscles need an energy surplus, fat loss requires a deficit, and doing both at once is supposedly a contradiction. The statement sounds logical. It is still too simplistic.
Your body does not keep a single energy account. It distributes building blocks between tissues, and that distribution responds to stimuli. A strength-training stimulus tells your muscles that they are needed. A lack of energy in the system tells your fat tissue to release energy. Both signals can coexist.
The question is not wrong; the expectation about the pace is. Recomposition is not a fast way to achieve both, but a slow path toward something the scale reflects poorly. If you only want to maintain muscle rather than build it while in a deficit, you can find a different perspective on the same topic under losing weight without muscle loss. There, the focus is on maintenance; here, it is on building muscle while losing fat at the same time.
Key message
Building muscle and losing fat at the same time is not a yes-or-no question, but rather one of pace, starting point, and whether you measure your progress at all.
What the research says about recomposition
The review most frequently cited in exercise science on this topic comes from the Strength and Conditioning Journal. It challenges the assumption that recomposition is purely a beginner phenomenon.
Documented source
“Although many suggest that this only occurs in untrained/novice and overweight/obese populations, there is a substantial amount of literature demonstrating this body recomposition phenomenon in resistance-trained individuals.”
In essence: Recomposition is often attributed only to beginners and people with overweight, but there is also substantial evidence for it in resistance-trained individuals. The authors identify progressive resistance training and evidence-based nutritional strategies as the two decisive factors.
Barakat C et al., Strength and Conditioning Journal
Volume 42, Issue 5, pages 7 to 21, 2020
Two things about this. First, the study says nothing about how quickly this happens, and it does not specify an amount in kilograms. Second, the effect depends on two conditions, both of which require work: training that becomes harder over time and a diet that provides enough protein.
What this review explicitly does not say is the often-heard addition that recomposition works especially well after a longer training break. This interpretation is plausible because lost muscle returns faster than newly built muscle develops. It is not supported by this source, which is why it appears here without a citation.
Four numbers that set the framework
Before getting into individual levers, here are the four values that guide the rest of the article. Each comes from a named source with a year, and each refers to something you can calculate in everyday life.
0,8 g
Protein per kilogram of body weight per day, reference value for adults aged 19 to under 65. German Nutrition Society, derivation 2017.
1,62 g
Per kilogram per day. Above this total intake, the analysis showed no further increase in fat-free mass from resistance training. Morton et al., 2018.
2 days
Muscle-strengthening activity per week for all major muscle groups, classified as a strong recommendation. WHO guideline, Bull et al., 2020.
55 %
This is how much the proportion of fat in the weight lost decreased when the sleep opportunity was shortened from 8.5 to 5.5 hours. Nedeltcheva et al., 2010.
What is striking is what is missing from this series: a figure for monthly muscle gain. There is no reliable average because starting point, training age, and diet vary too widely. Anyone who gives you such a figure is giving you an expectation, not a reference value.
Who it is realistic for
The more fat reserves someone has, the more easily the body covers the energy gap from its own stores instead of drawing on muscle tissue. That is why beginners and people with significant overweight often see changes in both directions at once during the first few months.
The effect is narrower in people who do strength training. Their muscles respond less strongly to the same stimulus because they are familiar with it. The 2020 review by Barakat et al. notes that the effect is supported by evidence there as well. It does not say that it happens just as quickly there.
The framework in which this works at all is a moderate deficit. An overview of natural bodybuilding competition preparation recommends setting calorie intake so that body weight decreases by about 0.5 to 1 percent per week to preserve muscle mass (Helms et al., 2014). Its origin in competitive sport should be stated: This is not a recommendation for everyday life, but guidance from an environment where preserving muscle takes priority over everything else.
At a glance
Most likely in beginners and in people with overweight whose goal is strength. In trained individuals, it is supported by evidence, but progresses slowly. A deficit resulting in about 0.5 to 1 percent weight loss per week is considered the limit in competition preparation beyond which muscle mass suffers (Helms et al., 2014).
Levers 1 and 2: protein and amino acid status
Lever 1: protein intake in grams per kilogram
The reference value set by the German Nutrition Society is 0.8 grams of protein per kilogram of body weight per day for adults aged 19 to under 65; from age 65, the DGE gives an estimated value of 1.0 grams (derived in 2017). Important for the calculation: With a BMI over 25, the DGE explicitly uses normal weight as the reference, not current weight.
The DGE also states that adult recreational athletes, meaning people completing four to five 30-minute sessions of moderate intensity per week, do not need increased protein intake. This is the reference value for a healthy population, not the target for building muscle while in a calorie deficit. The boundary and how to calculate your own amount are explained in the article how much protein for muscle building.
There is an upper point beyond which more no longer helps. An analysis of 49 studies with 1863 participants found that protein intake above 1.62 grams per kilogram per day produced no additional increase in fat-free mass from resistance training (Morton et al., 2018). Strength and fat-free mass increased measurably with additional protein, with the average increase in fat-free mass amounting to 0.30 kilograms.
The most frequently cited individual study on this topic comes from the American Journal of Clinical Nutrition. Young men, four weeks, an energy deficit of about 40 percent, resistance and interval training six days per week, plus 1.2 versus 2.4 grams of protein per kilogram. The group with the higher intake gained 1.2 kilograms of fat-free mass and lost 4.8 kilograms of fat, while the control group gained 0.1 kilograms and lost 3.5 kilograms (Longland et al., 2016). What this result is not: an everyday recommendation. Six training days with a 40 percent deficit for four weeks is a laboratory protocol, not a lifestyle model.
For food products, EU Regulation 432/2012 governs what may be claimed about protein. The approved wording is “Protein contributes to a growth in muscle mass,” and only for foods that meet the minimum requirements for being a source of protein. The statement describes a product; it is not a promise to you.
Lever 2: your amino acid status in the amino acid profile
The number of grams tells you how much protein was on your plate. It does not tell you how much of it reaches your bloodstream. That is precisely what an amino acid profile is for: a profile of individual amino acid levels from a blood sample. The sample is taken from capillary blood: a few drops from your fingertip that you collect yourself, unlike blood drawn from a vein by a doctor.
What an amino acid profile shows and what it does not
It shows your nutritional status
A profile of individual values from amino acid metabolism, including the nine essential amino acids that your body cannot produce itself.
It does not show training progress
An amino acid profile cannot show how much muscle you have built. For that, you need strength measurements over time and body composition data.
It responds to the last meal
Amino acid levels fluctuate significantly after eating. Without the fasting requirement from the instructions, you measure your breakfast rather than your nutritional status.
Four statements that persist
Each of these four statements is repeated in everyday training, and each contains a kernel of truth that has been overgeneralized. That is why, alongside the correction, this section also explains why the simplification seems so plausible.
Myth: Fat turns into muscle
The visible result leads to the conclusion that the body has been remodeled: less fat, more muscle, meaning that one developed from the other.
What holds true
They are two separate tissues and two separate processes that run in parallel. Fat tissue releases energy, while muscle incorporates protein. One does not transform into the other.
Myth: more protein, more muscle
Because protein is the building material, the calculation appears linear: twice the amount, twice the result.
What holds true
The curve levels off. Above 1.62 grams per kilogram per day, the analysis of 49 studies found no further increase in fat-free mass (Morton et al., 2018).
Myth: training is what matters, sleep is incidental
Training stimulus and nutrition can be planned; sleep feels like a residual factor that can be cut if necessary.
What holds true
With a shortened sleep opportunity, weight loss shifted away from fat and toward fat-free mass in the trial (Nedeltcheva et al., 2010).
Myth: it's all genetic
Anyone who progresses more slowly than others despite their efforts finds a convenient explanation in genetics and stops looking.
What holds true
The heritability of fat-free mass was estimated at 0.52 in a twin study (Arden and Spector, 1997). A proportion, not a verdict. The authors explicitly infer from this that there is room for lifestyle and intervention.
Levers 3 and 4: Sleep and cortisol
Lever 3: Hours in bed, not hours in the gym
The clearest figure in this article concerns not training. In a crossover trial with ten participants over 14 days of moderate calorie restriction, the sleep opportunity was varied between 8.5 and 5.5 hours. With the shorter duration, the proportion of fat in the weight lost fell by 55 percent, from 1.4 to 0.6 kilograms, while the loss of fat-free mass increased by 60 percent, from 1.5 to 2.4 kilograms (Nedeltcheva et al., 2010).
Ten participants is a small sample, and that belongs in the interpretation. The direction of the finding is nevertheless uncomfortably clear: The same calorie balance led to a different body-composition outcome depending on sleep duration. Anyone who wants both at the same time while sleeping five hours is working against themselves. How sleep and metabolism are connected is described in more detail in the article Sleep and Metabolism Explained Simply.
Lever 4: Cortisol as a data point, not a verdict
In the 2016 study by Longland et al., there was a secondary finding that is rarely cited: changes in blood cortisol were associated with changes in body fat and fat-free mass. An association is not causation, and the values were in the moderate range of statistical significance. It remains noteworthy that a stress hormone appeared in a training study at all.
The mechanism behind this is described. A review in the International Journal of Biochemistry and Cell Biology summarizes that muscle loss under glucocorticoids results from increased protein breakdown and reduced protein synthesis (Schakman et al., 2013). This work explicitly concerns strongly elevated glucocorticoid levels in disease states. It says nothing about everyday stress and cannot be applied to a single value from your daily life.
In practical terms, a cortisol level is a data point at a specific time, not a diagnosis or an explanation for a lack of progress. How such a measurement works at home and what it can tell you is explained under Measuring cortisol at home. At mybody®x (MYBODY Lab GmbH), the Men's Wellness Check and the Women's Wellness Check include ferritin and vitamin D in addition to cortisol, meaning three values that regularly come up in connection with stress and fatigue. Both provide a cortisol level at the time of sampling, not a daily profile.
The six levers made measurable
This overview is the core of the article. For each lever, it shows the value, the tool, the sensible interval between two measurements, and the limit of what the result can tell you. The last column is the most important: It prevents you from reading more into a number than it can actually tell you.
| Levers | What you measure | With what | When to test | What the value does not tell you |
|---|---|---|---|---|
| 1 Protein intake | Grams of protein per kilogram of body weight per day | Scales and a log covering three to seven typical days | Once at the beginning, then after every weight change of several kilograms | Nothing about how well your body utilizes the protein |
| 2 Amino acid status | Profile of individual amino acid levels in the blood | Aminogram from fasting capillary blood | At the beginning, follow-up after six to twelve months | Nothing about your training progress and nothing about the right amount of food |
| 3 Sleep | Hours of sleep opportunity per night | Log over two weeks, bedtime and wake-up time | Ongoing, because the value shifts from week to week | Nothing about sleep quality and nothing about a sleep disorder |
| 4 Cortisol and recovery | Cortisol level at the time of sampling | Capillary blood test, together with ferritin and vitamin D | If exhaustion persists, repeat no sooner than after several months | Nothing about your daily pattern, nothing about an illness, no diagnosis |
| 5 strength-training days | Training days per week involving all major muscle groups | Calendar or training log, counted over four weeks | Monthly, looking back rather than based on intention | Nothing about the quality of the sessions and nothing about progressive overload |
| 6 Genetic predisposition | Genetic predispositions for muscle fiber type, recovery, and nutrient requirements | DNA report from a saliva sample | Once, because DNA does not change | Nothing about your outcome. Genetic makeup is a probability across groups, not a fixed destiny for you |
Levers 5 and 6: strength-training days and genetic makeup
Lever 5: two days are the lower limit, not the goal
The WHO guideline on physical activity recommends that adults perform muscle-strengthening activities involving all major muscle groups on two or more days per week, and classifies this as a strong recommendation (Bull et al., 2020). This recommendation is for general health. For recomposition, it is the lower limit, below which the stimulus needed to direct the building material into the muscles is missing.
Which exercises you do is deliberately not specified here. The measurable value is the number of strength-training days per week, counted retrospectively. Anyone averaging 1.3 days over four weeks does not have a nutrition problem, but a counting problem that was previously easy to hide.
Lever 6: genetic makeup is not a fixed destiny
How much of body composition is attributable to genetic predisposition at all has been estimated several times. A twin study of 706 postmenopausal women found heritability of 0.52 for fat-free mass, 0.46 for leg extension strength, and 0.30 for grip strength (Arden and Spector, 1997). The authors explicitly conclude that there is room for lifestyle and intervention.
The HERITAGE Family Study found a maximum heritability of 62 percent for body fat percentage and, depending on the model, 39 to 65 percent for fat-free mass (Rice, Bouchard et al., 1997). In this context, familial means genetic factors plus shared environment, including the dining table at which someone grew up. Anyone who wants to read more about the processes behind this can find them under Metabolism and Fat Burning.
Your genetic makeup is not a fixed destiny. It explains why your path looks different from someone else’s, not where it ends.
Who can benefit from a test
A test does not replace any of the six levers. It only answers one question you would otherwise estimate. Four of the six values cost you nothing but attention: grams, hours, training days, and weight trend. Two require a lab.
Makes sense for you if …
You are just starting out or have been training regularly with weights for less than a year and want to know where your nutritional status stands before adjusting your diet.
You are returning after a longer break. This group appears promising, but has not been specifically studied in the evidence used here.
You are overweight and pursuing a strength goal, not just a weight goal on the scale.
Probably not if …
You are pursuing a competition goal and working with a coach. In that case, your progress is already being monitored more closely than a self-test can reflect.
You are underweight. Then the priority is overall weight gain, which requires medical supervision.
You have a history of an eating disorder. Values and numbers can narrow rather than broaden your perspective on your body.
You are pregnant or breastfeeding. A calorie deficit is then not a topic for a guide article, but for your doctor.
What the tests measure
Two tests in the mybody®x product range relate to levers 2 and 6. One measures your current status, the other your predisposition. They answer different questions, and neither builds muscle.
Blood test from capillary blood
PerformanceCheck | Amino Acid Test
An amino acid profile with 22 values from amino acid metabolism, including all nine essential amino acids. What the test does not do: It does not tell you how much protein you should eat, and it does not make any muscle bigger. The values fluctuate significantly depending on your last meal, which is why the fasting requirement in the instructions applies.
Laboratory analysis 3–5 business days after sample receipt
DNA test from saliva
Fitness | VITALITY DNA Test
Over 100 genetic variations from a saliva sample, 32 analysis reports in 6 chapters across 160 pages, plus an assessment of over 1,000 foods. Selected SNPs are examined, meaning individual inheritable sections of your DNA. What the test does not do: It does not build muscle and does not predict your results. It describes predispositions, not destiny.
Laboratory analysis 15–25 business days after sample receipt
The similarity in names to other products in the range is coincidental and regularly causes confusion. The PerformanceCheck is a blood test and shows your status today. The Fitness VITALITY DNA Test is a saliva test and shows a predisposition that does not change. DNA explains the why, blood the now.
Limitations: what numbers cannot tell you
The most honest limitation first: None of the six values tells you whether recomposition is currently taking place in your body. That would require repeated body-composition measurements under the same conditions, and neither a bathroom scale nor a lab report provides that. The six values tell you something else: whether the prerequisites are in place.
The second limitation lies in the studies themselves. Ten participants in the sleep trial, young men under laboratory conditions in the protein study, postmenopausal women in the twin study: Each of these groups represents a subset, not the general population. What can be generalized is the direction, not the exact value.
The third limitation concerns the tests. An amino acid profile shows a snapshot of your nutritional status. A DNA report describes probabilities in population groups. Both help you justify decisions more effectively. Neither is an examination that establishes or rules out a disease.
When to have it medically evaluated
Unintentional weight loss
If your weight is dropping even though you have not changed anything, that belongs in a doctor's office, not in a training plan.
Rapidly occurring loss of strength
A significant drop in performance within a few weeks is not a motivation issue and should be professionally assessed.
Exhaustion that dominates everyday life
Persistent exhaustion can have many possible causes. A self-test can help prepare for a conversation, but it cannot replace one.
What you can do differently tomorrow
At the beginning was the question of whether you had to choose. The answer is no, but it comes with a condition that is rarely included: You have to stop reading progress from a single number. A scale that remains unchanged for four weeks can mean stagnation or exactly the opposite.
What is new about this perspective is the order. Most people start with Lever 1 and stay there because nutrition feels most like taking action. It is more effective to count the two levers that cost nothing and are most often the cause first: hours of sleep and strength-training days. Only when those are in order is it worth looking at lab results.
Give it four weeks and record two numbers: how many hours you slept and on how many days you trained with weights. After that, you will know more about your progress than any scale can tell you. And when you reach the point where you want to know what your nutritional status really looks like, measure it instead of guessing.
Frequently asked questions
How long does it take for something to show?
There is no reliable average figure per month because starting points vary too widely. The length of the study serves as a guide: the often-cited trial by Longland et al. in 2016 lasted four weeks under laboratory conditions, with six training days per week. In everyday life, with two to three strength-training days, you should think in months rather than weeks, and you will notice progress first in strength measurements, not on the scale.
Do I absolutely need a calorie deficit for recomposition?
Fat loss requires a negative energy balance; otherwise, fat tissue will not release anything. The question is how large the deficit should be. Natural contest preparation provides the guideline of losing around 0.5 to 1 percent of body weight per week to preserve muscle (Helms et al., 2014). Based on experience, those who lose weight faster also lose more fat-free mass. A deficit without strength training leads in the same direction.
Is protein powder enough to meet my needs?
Powder is a convenient serving of protein, nothing more. What matters is the daily amount in grams per kilogram, regardless of whether it comes from quark, lentils, or a shaker. Above 1.62 grams per kilogram per day, the analysis of 49 studies involving 1,863 participants found no further increase in fat-free mass (Morton et al., 2018). If you reach this amount through regular meals, you gain nothing from additional powder.
How often should I have my amino acid levels measured?
A blood value reflects your current status and changes over several months. One measurement at the beginning and a follow-up after six to twelve months are generally sufficient if something has changed in your diet or training load in the meantime. Measuring more often mainly adds noise because the values respond strongly to your last meal. The fasting requirement in the instructions determines comparability.
Can I recognize recomposition on the scale?
Hardly at all, and that is the most common reason for stopping prematurely. When fat mass decreases and fat-free mass increases, the two changes partially offset each other in total body weight. More meaningful are strength measurements recorded over several weeks, how your clothes fit, and measurements of your circumference at the same points and at the same time of day. The scale remains useful, but as one of several numbers, not as a verdict.
Next step
Count first, then measure
If you know your hours of sleep and strength-training days and want to know where your nutritional status stands, an amino acid profile is the next step.
View PerformanceCheck View the fitness DNA testRead more
You might also be interested in this
Which factors a fitness DNA report describes and where its significance ends.
Why body composition says more about progress than total weight.
Sources
- German Nutrition Society: Protein reference values (derivation 2017) - dge.de
- Morton RW et al.: British Journal of Sports Medicine 52(6):376–384 (2018) - pubmed.ncbi.nlm.nih.gov
- Longland TM et al.: American Journal of Clinical Nutrition 103(3):738–746 (2016) - pubmed.ncbi.nlm.nih.gov
- Nedeltcheva AV et al.: Annals of Internal Medicine 153(7):435–441 (2010) - pubmed.ncbi.nlm.nih.gov
- Bull FC et al. (WHO): British Journal of Sports Medicine 54(24):1451–1462 (2020) - pubmed.ncbi.nlm.nih.gov
- Barakat C et al.: Strength and Conditioning Journal 42(5):7–21 (2020) - doi.org
The protein reference values and the statement about recreational athletes are based on [1], the plateau at 1.62 grams per kilogram on [2], the four-week study on protein during a calorie deficit, including the secondary cortisol finding, on [3], the sleep figures on [4], the two strength-training days per week on [5], and the assessment of who benefits on [6]. Also documented in the text and cited with the year: Helms ER, Aragon AA, Fitschen PJ, Journal of the International Society of Sports Nutrition (2014) on a deficit of 0.5 to 1 percent per week; Schakman O et al., International Journal of Biochemistry and Cell Biology (2013) on the mechanism under glucocorticoids; Arden NK and Spector TD, Journal of Bone and Mineral Research (1997), and Rice T, Bouchard C et al., HERITAGE Family Study, Obesity Research (1997) on heritability; Regulation (EU) No. 432/2012 on the authorized wording regarding proteins. All sources were accessed on 08.09.2026. Product information, prices, and images are from the mybody®x product pages, as of 08.09.2026.
mybody®x editorial & expert team
Sports and exercise Protein and amino acids Blood values and DNA
This article was created by the mybody®x editorial and expert team and checked against the primary sources cited. The people behind it are listed on the authors page.
Published on 08.09.2026 · Last updated on 08.09.2026
Our products are not intended to diagnose, treat, cure, or prevent diseases. The content is for general information only and does not replace medical advice, diagnosis, or treatment. Reference ranges depend on the laboratory, method, and age; the information on your report is always authoritative. The DNA analysis is intended for nutritional and lifestyle advice. It is not a diagnostic procedure, does not predict disease, and does not replace a medical examination or advice. Genetic variants describe probabilities in population groups, not fixed outcomes for individuals.
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