Building muscle and losing fat at the same time: is it possible? Six measurable levers
ca. 24 Minuten
The essentials
Yes, it’s possible to do both at once. In sports science, the process is called body recomposition, meaning building muscle while losing fat. It tends to work best for beginners and people with overweight. It has also been documented in people who strength train, but it happens slowly (Barakat et al., 2020).
The catch isn’t whether it’s possible, but that you’ll hardly notice it. The scale barely moves because two processes are working against each other. If you track only your weight, you’ll mistake progress for a plateau and give up. That’s why this article gives each of the six levers a value you can track.
Chapters 2 and 3 cover the research and four key numbers. Chapter 4 explains who it’s realistic for. The levers are covered in chapters 5, 7, and 9, with an overview in chapter 8. Chapter 12 outlines the limitations. You won’t find a workout or nutrition plan here.
What to expect in this article
1. Can you do both at once, or do you have to choose?
2. What research says about recomposition
3. Four numbers that set the parameters
4. Who it’s realistic for
5. Levers 1 and 2: protein and amino acid status
6. Four stubborn myths
7. Levers 3 and 4: sleep and cortisol
8. Measuring the six levers
9. Levers 5 and 6: strength-training days and genetics
10. Who can benefit from a test
11. What different tests measure
12. Limitations: what numbers can’t tell you
13. What you can do differently tomorrow
Frequently asked questions
Sources
Can you do both at once, or do you have to choose?
The rule passed around in every gym goes like this: bulk first, then define. Muscles need an energy surplus, fat loss needs a deficit, and doing both at once is supposedly a contradiction. It sounds logical. Still, it’s an oversimplification.
Your body doesn’t keep just one energy account. It distributes building blocks among tissues, and that distribution responds to stimuli. A strength-training stimulus tells your muscles they’re needed. A lack of energy in the system tells your fat tissue to release some. Both signals can coexist.
The question isn’t wrong; the expectation about the pace is. Recomposition isn’t a fast way to achieve both, but a slow way to reach something the scale doesn’t reflect well. If you only want to maintain muscle in a deficit, not build it, you’ll find another perspective on the same topic in losing weight without muscle loss. That article is about maintenance; this one is about building muscle while losing fat.
Key takeaway
Building muscle and losing fat at the same time isn’t a yes-or-no question, but one of pace, starting point, and whether you’re measuring progress at all.
What research says about recomposition
The review most often cited on this topic in exercise science comes from the Strength and Conditioning Journal. It challenges the assumption that recomposition is exclusively 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 it has also been documented extensively in people trained in resistance exercise. The authors identify progressive resistance training and evidence-based nutrition strategies as the two key factors.
Barakat C et al., Strength and Conditioning Journal
Volume 42, Issue 5, pages 7 to 21, 2020
Two points on this. First, the paper says nothing about how long it takes and gives no amount in kilograms. Second, the effect depends on two conditions, both of which require work: training that gets harder over time, and a diet that provides enough protein.
What this review does not explicitly say is the often-heard claim that recomposition works especially well after a long break from training. This is plausible because lost muscle returns faster than new muscle is built. But this source does not substantiate the claim, so it appears here without a citation.
Four figures that set the framework
Before we get into individual factors, here are the four figures that frame the rest of the article. Each comes from a named source with a year, and each describes something you can track 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, 2017 derivation.
1,62 g
Per kilogram per day. Above this total intake, the analysis found no further increase in lean mass from resistance training. Morton et al., 2018.
2 days
Minutes per week of muscle-strengthening activity for all major muscle groups, classified as a strong recommendation. WHO guidelines, Bull et al., 2020.
55 %
How much the proportion of weight lost as fat declined when sleep opportunity was reduced from 8.5 to 5.5 hours. Nedeltcheva et al., 2010.
What stands out is what’s missing from this list: a figure for monthly muscle gain. There is no reliable average because starting points, training experience, and nutrition vary too widely. Anyone who gives you such a figure is stating an expectation, not a reference value.
Who it’s realistic for
The more fat reserves you have, the more easily the body can cover the energy gap from its own stores instead of drawing on muscle. That is why beginners and people who are significantly overweight often see changes in both directions at once during the first few months.
The effect is more limited in people who train for strength. Their muscles respond less strongly to the same stimulus because they are familiar with it. Barakat et al.’s 2020 review notes that the effect has also been demonstrated in this group. It does not say that it happens just as quickly.
The conditions under which this works at all include 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 origins in competitive sports should be noted: This is not a recommendation for everyday life, but a guideline from an environment where preserving muscle takes priority over everything else.
At a glance
Most likely for beginners and for people who are overweight and aiming to build strength. Proven in trained individuals, but slow. 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 German Nutrition Society’s reference value is 0.8 grams of protein per kilogram of body weight per day for adults aged 19 to under 65; for those aged 65 and over, the DGE gives an estimated value of 1.0 grams (2017 derivation). Important for the calculation: For a BMI over 25, the DGE explicitly uses normal weight as the reference, not current weight.
The German Nutrition Society also notes that recreational athletes, meaning people who do four to five 30-minute sessions at 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 in a deficit. The article how much protein for building muscle explains where this limit lies and how to calculate your own amount.
There’s a point beyond which more doesn’t help. An analysis of 49 studies involving 1,863 participants found that protein intake above 1.62 grams per kilogram per day led to no further gains in lean mass from strength training (Morton et al., 2018). Strength and lean mass increased measurably with additional protein, with an average lean mass gain of 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, strength and interval training six days a week, and 1.2 versus 2.4 grams of protein per kilogram. The group with the higher intake gained 1.2 kilograms of lean 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 a week at a 40 percent deficit for four weeks is a laboratory protocol, not a lifestyle.
For food products, EU Regulation 432/2012 sets out what can be said about protein. The approved wording is “Protein contributes to an increase in muscle mass,” and it can be used only for foods that meet the minimum requirements for being a source of protein. This is a claim about a product, not a promise to you.
Lever 2: your amino acid status in the aminogram
The number of grams tells you how much protein was on your plate. It doesn’t tell you how much of it makes it into your blood. That’s exactly what the aminogram is for: a profile of individual amino acid levels from a blood sample. The test uses capillary blood: a few drops from your fingertip that you collect yourself, unlike a blood draw from a vein at the doctor’s office.
What an aminogram does and doesn’t show
It shows your nutritional status
A profile of individual values related to amino acid metabolism, including the nine essential amino acids your body can’t produce itself.
It doesn’t show your training progress
You can’t tell from an aminogram how much muscle you’ve built. For that, you need to track strength over time and assess your body composition.
It responds to your last meal
Amino acid levels fluctuate considerably after eating. If you don’t follow the fasting instructions, you’ll be measuring your breakfast rather than your nutritional status.
Four statements that just won’t go away
Each of these four statements gets repeated in everyday training, and each has a kernel of truth that has been overgeneralized. That’s why, alongside the correction, this article also explains why the oversimplification seems so plausible.
Myth: Fat turns into muscle
People infer a transformation from the visible result: less fat, more muscle, so one must have come from the other.
What’s true
These are two separate tissues and two separate processes that happen in parallel. Fat tissue releases energy; muscle builds protein. One does not turn into the other.
Myth: More protein, more muscle
Since protein is the building material, the calculation seems linear: twice as much, twice the result.
What’s true
The curve levels off. Above 1.62 grams per kilogram per day, an analysis of 49 studies found no further increase in fat-free mass (Morton et al., 2018).
Myth: Training is what matters; sleep is secondary
Training stimulus and nutrition can be planned; sleep feels like a leftover variable that can be cut if necessary.
What’s true
With shorter sleep opportunity, the trial found that weight loss shifted away from fat and toward fat-free mass (Nedeltcheva et al., 2010).
Myth: It’s all down to genetics
If someone makes slower progress than others despite putting in the effort, genetics offers a convenient explanation—and they stop looking for answers.
What’s true
The heritability of fat-free mass was estimated at 0.52 in a twin study (Arden and Spector, 1997). A contribution, not a verdict. The authors explicitly conclude that this leaves 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 is not about training. In a crossover trial with ten participants over 14 days of moderate calorie restriction, sleep opportunity was varied between 8.5 and 5.5 hours. With the shorter duration, the proportion of weight loss from fat fell by 55 percent, from 1.4 to 0.6 kilograms, and 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 should be kept in perspective. Still, the direction of the finding is uncomfortably clear: the same calorie balance led to a different body composition outcome depending on sleep duration. Trying to achieve both while sleeping five hours works against you. The relationship between sleep and metabolism is explained in more detail in Sleep and Metabolism Explained Simply.
Lever 4: Cortisol as a data point, not a verdict
A secondary finding in the 2016 study by Longland et al. is rarely cited: changes in blood cortisol were associated with changes in body fat and lean mass. An association is not causation, and the values were in the middle range of statistical significance. It is still noteworthy that a stress hormone showed up at all in a training study.
The mechanism behind this has been described. A review in the International Journal of Biochemistry and Cell Biology summarizes that muscle wasting under glucocorticoids results from increased protein breakdown and reduced protein synthesis (Schakman et al., 2013). This study specifically concerns strongly elevated glucocorticoid levels in disease states. It does not make a claim about everyday stress, and it cannot be applied to a single value from your daily life.
In practice, a cortisol value is one data point at one point in time, not a diagnosis or an explanation for a lack of progress. For details on how this measurement works at home and what it can tell you, see 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 as well as cortisol, so they cover three values that regularly come up in discussions of strain and fatigue. Both provide a cortisol value at the time the sample is taken, not a daily profile.
The six levers, made measurable
This overview is the core of the article. It shows, for each lever, the value, the method, the recommended interval between measurements, and the limits of what it tells you. The last column is the most important: it prevents you from reading more into a number than it can tell you.
| Levers | What you measure | With what | When to check | What the value does not tell you |
|---|---|---|---|---|
| 1 Protein intake | Grams of protein per kilogram of body weight per day | Scales and a record of three to seven typical days | Once at the start, then whenever your weight changes by several kilograms | Nothing about how well your body uses protein |
| 2 Amino acid status | Profile of individual amino acid levels in the blood | Amino acid profile from capillary blood, collected while fasting | At the start, with a follow-up after three to six months | Nothing about your training progress or the right amount of food |
| 3 Sleep | Hours of sleep opportunity per night | Two-week record of bedtime and wake-up time | Ongoing, because the value changes from week to week | Nothing about sleep quality or a sleep disorder |
| 4 Cortisol and recovery | Cortisol level at the time of sampling | Capillary blood test, together with ferritin and vitamin D | For persistent fatigue, repeat no sooner than after several months | Nothing about your daily patterns or any illness, and 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 relying on intentions | Nothing about the quality of your sessions or progression of your training load |
| 6 Predisposition | Predispositions related to muscle fiber type, recovery, and nutrient requirements | DNA report from a saliva sample | Once, because your DNA doesn’t change | Nothing about your outcome. A predisposition is a probability across groups, not a certainty for you |
Levers 5 and 6: strength-training days and predisposition
Lever 5: two days are the lower limit, not the goal
The WHO guidelines on physical activity recommend that adults do muscle-strengthening activities involving all major muscle groups on two or more days a week, and classify this as a strong recommendation (Bull et al., 2020). This recommendation is for general health. For recomposition, it’s the lower limit; below it, the stimulus needed to direct the building blocks to the muscles is missing.
The exercises you do are deliberately not listed here. The measurable figure is the number of strength-training days per week, counted retrospectively. If your average over four weeks is 1.3 days, you don’t have a nutrition problem, but a counting problem that was easy to hide before.
Lever 6: predisposition is not destiny
Body composition heritability has been estimated several times. A twin study of 706 postmenopausal women found heritability estimates 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 changes and intervention.
The HERITAGE Family Study found a maximum heritability of 62 percent for body fat percentage, and 39 to 65 percent for fat-free mass, depending on the model (Rice, Bouchard et al., 1997). In this study, familial means genetics plus shared environment, including the dinner table someone grew up around. Those who want to read about the underlying processes can find them under Metabolism and Fat Burning.
Your predisposition isn’t 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 doesn’t replace any of the six levers. It only answers a question you’d otherwise be guessing about. Four of the six metrics cost you nothing but attention: grams, hours, training days, and weight trends. Two require a lab.
It makes sense for you if …
You’re starting out or have been training regularly with weights for less than a year, and want to know where your nutritional status stands before changing your diet.
You’re returning after a long break. This group is considered promising, but it has not been specifically studied in the evidence used here.
You’re overweight and have a strength goal, not just a target weight on the scale.
Probably not if …
You have a competition goal and work with a coach. They’ll be monitoring you more closely than a self-test can anyway.
You’re underweight. The priority then is to build up overall, and that should be done under medical supervision.
You have a history of an eating disorder. Values and numbers can narrow your perspective on your body instead of broadening it.
You’re pregnant or breastfeeding. A calorie deficit isn’t a topic for an advice article then; it’s something to discuss with your doctor.
What each test measures
Two tests in the mybody®x range address levers 2 and 6. One measures your current status, the other your predisposition. They answer different questions, and neither builds muscle.
Capillary blood test
PerformanceCheck | Amino Acid Test
An amino acid profile with 22 values from amino acid metabolism, including all nine essential amino acids. What the test doesn’t do: it doesn’t tell you how much protein to eat, and it won’t build muscle for you. The values fluctuate considerably depending on your last meal, so follow the fasting instructions in the guide.
Lab analysis 3–5 business days after sample receipt
DNA test from saliva
Fitness | VITALITY DNA test
Over 100 gene variants from a single saliva sample, 32 analysis reports in 6 chapters across 160 pages, plus an assessment of over 1,000 foods. The test examines selected SNPs, or individual inherited sections of your DNA. What the test doesn't do: build muscle or predict your results. It describes predispositions, not certainties.
Lab analysis 15–25 business days after sample receipt
The similarity in name 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 doesn't change. DNA explains the why; blood shows the now.
Limitations: what numbers can't tell you
The most honest limitation first: None of the six values tells you whether recomposition is happening right now. That would require repeated body composition measurements under the same conditions, and neither a bathroom scale nor a lab report can provide that. The six values tell you something else: whether the conditions are right.
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. The findings are applicable in terms of direction, not exact values.
The third limitation concerns the tests. An amino acid profile shows a snapshot of your nutrient status. A DNA report describes probabilities across population groups. Both can help you make better-informed decisions. Neither is a test that diagnoses or rules out a disease.
When to consult a doctor
Unintentional weight loss
If your weight is dropping even though you haven’t changed anything, that’s something to discuss with a doctor, not address with a training plan.
Rapid loss of strength
A sharp drop in performance over a few weeks isn’t a motivation issue and should be assessed by a professional.
Fatigue that disrupts daily life
Ongoing fatigue can have many possible causes. A self-test can help you prepare for a conversation, but it can’t replace one.
What you can do differently tomorrow
It started with the question of whether you have to choose. The answer is no, but it comes with a condition that is rarely mentioned: you have to stop judging progress by a single number. A scale that doesn’t budge for four weeks could mean you’ve stalled, or it could mean exactly the opposite.
What’s new about this perspective is the order. Most people start with lever 1 and stay there, because nutrition feels most like taking action. A more effective approach is to first count the two levers that cost nothing and are most often the cause: hours of sleep and strength-training days. Only once those are in place is it worth looking at lab results.
Give yourself four weeks and track two numbers: how many hours you slept and how many days you trained with weights. After that, you’ll know more about your progress than any scale can tell you. And when you reach the point where you want to know what your nutrient levels really look like, measure them instead of guessing.
Frequently asked questions
How long does it take to see results?
There is no reliable average figure per month, because starting points vary too widely. The study duration offers a guide: the often-cited 2016 trial by Longland et al. ran for four weeks under laboratory conditions, with six training days per week. In everyday life, with two to three strength-training days, think in months rather than weeks, and look for progress first in your strength numbers, not on the scale.
Do I absolutely need a calorie deficit for recomposition?
Fat loss requires a negative energy balance; otherwise, fat tissue won’t release anything. The question is how large the deficit should be. Guidance from natural contest preparation suggests losing about 0.5 to 1 percent of body weight per week to preserve muscle (Helms et al., 2014). People who lose weight faster tend to lose more lean mass as well. 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, an analysis of 49 studies with 1,863 participants found no further increase in lean mass (Morton et al., 2018). If you reach that amount through regular meals, additional powder offers no benefit.
How often should I get my amino acid levels tested?
A blood test reflects your current status and changes over several months. In most cases, one test at the start and a follow-up after three to six months are enough if your diet or training load has changed in the meantime. Testing more often mainly adds noise, because the results are highly responsive to your last meal. Follow the fasting instructions in the guide to ensure the results are comparable.
Can I tell if I’m recomping by looking at the scale?
Hardly, and that’s the most common reason for quitting early. When fat mass decreases and lean mass increases, the two changes partially offset each other in your total weight. More informative are strength metrics tracked over several weeks, how your clothes fit, and measurements taken at the same spots at the same time of day. The scale is still useful, but as one of several figures, not as a verdict.
Next step
Count first, then measure
Once you’ve established your sleep hours and strength-training days and want to know where your nutrient levels stand, the aminogram is the next step.
View PerformanceCheck View Fitness DNA TestRead more
You might also be interested in
What a fitness DNA report describes and where its insights end.
Why body composition says more about progress than total weight.
Sources
- German Nutrition Society: Reference Values for Protein (2017 derivation) – 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 reference values for protein 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 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 cited in the text with publication 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 about protein. All sources were accessed on 08.09.2026. Product details, prices, and images are from 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 editorial and expert team at mybody®x and checked against the primary sources cited. Find out who is behind it 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 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. DNA analysis is intended to provide nutrition and lifestyle advice. It is not a diagnostic procedure, does not predict disease, and does not replace a medical examination or consultation. Genetic variants describe probabilities in population groups, not a predetermined outcome for individuals.
