Study analysis · European Journal of Applied Physiology · 2026
You can lose fat and gain muscle at the same time—even without a calorie deficit. Here's how.
Eating a high-protein diet (2.5g per kg of body weight) while lifting weights for 10 weeks helped people lose fat and gain muscle, even if they ate just enough calories to maintain their weight.
Overview
What the study found
The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.
In simple terms
This study is like a science experiment where people were randomly put into groups to try different diets. Because it's a randomized experiment, we can say the diet caused the changes, but we need to be careful because the study was small and not everyone knew which group they were in. So we can say the diet might cause changes, but we're not 100% sure.
What’s the bottom line?
Researchers tested two diets with lots of protein (2.5 grams per kilogram of body weight) plus weight training for 10 weeks. One group ate enough calories to stay the same weight, another ate 250 calories less per day, and a third group just trained without diet advice. Both diet groups gained muscle and lost fat, but the group eating fewer calories lost more fat. The group without diet advice didn't change.
How strong is this study?
The study was pretty well done because it had a control group and used a special machine to measure body fat and muscle. But it had some problems: only 30 people took part, and we don't know if they actually ate what they were told. So the results are good but not super strong, and we shouldn't trust them completely.
40 / 100
- COI disclosure+40/40
- Data availabilitydata not shared
- Code availabilitycode not shared
60 / 100
- Randomization+20/20
- Blindingblinding unclear
- Control group+15/15
- Sample size (n=30)+2.8/20
- Follow-up+10/10
100 / 100
77 / 100
- P-values+15/15
- Effect size+20/20
- Confidence intervals+15/15
- Pre-registrationnot pre-registered
Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.
Where it sits
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 568 / 100
Probability of being correct
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
This design can establish causation. Although this is an RCT, the small sample size (n=30), lack of blinding, and unquantified dietary adherence limit the strength of causal inferences. The results are specific to this population and may not generalize.
COI Unknown
Could not determine conflict of interest status
No conflicts of interest declared; funding information not provided.
The study text does not include a conflict of interest statement or funding declaration. Author affiliations are not provided.
Key takeaways
- 01
The deficit group lost about 2.94 kg (6.5 pounds) of fat and gained about 1.04 kg (2.3 pounds) of muscle.
- 02
The isocaloric group lost about 1.41 kg (3.1 pounds) of fat and gained about 0.97 kg (2.1 pounds) of muscle.
- 03
The control group had no significant changes.
- 04
These are absolute changes over 10 weeks.
- 05
The deficit group lost about 2.94 kg of fat (roughly 6.5 pounds) and gained about 1.04 kg of muscle (about 2.3 pounds).
- 06
The isocaloric group lost about 1.41 kg of fat (about 3.1 pounds) and gained 0.97 kg of muscle (about 2.1 pounds).
- 07
The absolute difference in fat loss between the deficit and isocaloric groups was about 1.53 kg (about 3.4 pounds).
Surprising findings
- Body recomposition is possible even without a calorie surplus.Conventional wisdom says you need a surplus to build muscle and a deficit to lose fat. This study shows both can happen simultaneously with high protein and training.
- The deficit group lost twice as much fat as the isocaloric group, but gained the same amount of muscle.You might expect that eating fewer calories would impair muscle growth, but the muscle gain was nearly identical (1.04 kg vs 0.97 kg).
- The control group, which trained without dietary supervision, saw no significant changes in body composition.Many people believe that just lifting weights will change their body, but without proper nutrition, results are minimal. This highlights the importance of diet.
Practical takeaways
Consume around 2.5 g of protein per kg of body weight daily if you're resistance training and want to recompose your body.
This is a high intake; ensure it fits your overall calorie goals and doesn't cause digestive issues.
Medium (based on this small study, but consistent with other research) confidenceIf you want to lose fat while maintaining muscle, aim for a modest calorie deficit of about 250-500 kcal below maintenance, combined with high protein and resistance training.
The study used a 250 kcal deficit; larger deficits might impair muscle gain.
Medium confidenceDon't neglect nutrition even if you train regularly; without proper dietary guidance, training alone may not change your body composition.
This is based on the control group's lack of changes, but they also didn't have supervision, so motivation might be a factor.
High (common sense, but supported by this study) confidenceWhy this study matters
Body Recomposition: The Myth of the Calorie Surplus
This study shows that resistance-trained individuals can gain lean mass and lose fat simultaneously, even when eating at maintenance calories. The isocaloric group gained 0.97 kg of fat-free mass and lost 1.41 kg of fat (though the fat loss wasn't statistically significant). The deficit group lost 2.94 kg of fat and gained 1.04 kg of muscle.
It challenges the traditional belief that you need a calorie surplus to build muscle and a deficit to lose fat. This suggests that with high protein and training, you can do both at once.
Protein: The Key to Simultaneous Fat Loss and Muscle Gain
Both groups consumed 2.5 g/kg/day of protein, which is above the recommended 1.6-2.2 g/kg for muscle growth. This high protein intake likely helped preserve and build muscle even in a calorie deficit. The deficit group lost twice as much fat as the isocaloric group (2.94 kg vs 1.41 kg) while gaining similar muscle (1.04 kg vs 0.97 kg).
Protein is often seen as just for muscle, but it also helps with fat loss by increasing satiety and thermic effect. This study shows that high protein can support recomposition.
The Control Group: Why Training Alone Isn't Enough
The control group did the same resistance training but without dietary supervision. They showed no significant changes in body composition: fat mass changed by -0.15 kg and fat-free mass by +0.02 kg. This highlights that nutrition is crucial for body composition changes, even with training.
Many people think just lifting weights will change their body, but without proper nutrition, results are minimal. This emphasizes the importance of diet.
Moderate Deficit: The Sweet Spot for Fat Loss
The deficit group consumed 250 kcal less per day than maintenance. This modest deficit led to a significant fat loss of 2.94 kg over 10 weeks, while still gaining 1.04 kg of muscle. The isocaloric group lost only 1.41 kg of fat (not significant) but gained similar muscle.
A small calorie deficit can lead to significant fat loss without sacrificing muscle gains, making it a practical approach for body recomposition.
The Energy Balance Model: Is It Too Simple?
The study challenges the traditional calories-in/calories-out model by showing that body recomposition can occur in energy balance. The authors argue that the energy density of fat vs muscle (9.4 kcal/g vs 1.8 kcal/g) means you can lose fat and gain muscle without a net calorie deficit.
This is a controversial topic in nutrition science. It suggests that macronutrient composition and training stimulus matter more than just total calories.
Want the whole report?
Detailed mode opens the full scientific breakdown — every score component, the methodology, conflicts of interest, the evidence analysis behind each claim, and the raw study data.
Overview
What the study found
The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Researchers tested two diets with lots of protein (2.5 grams per kilogram of body weight) plus weight training for 10 weeks. One group ate enough calories to stay the same weight, another ate 250 calories less per day, and a third group just trained without diet advice. Both diet groups gained muscle and lost fat, but the group eating fewer calories lost more fat. The group without diet advice didn't change.
Research results
The deficit group lost about 2.94 kg (6.5 pounds) of fat and gained about 1.04 kg (2.3 pounds) of muscle. The isocaloric group lost about 1.41 kg (3.1 pounds) of fat and gained about 0.97 kg (2.1 pounds) of muscle. The control group had no significant changes.
What this means - more context
These are absolute changes over 10 weeks. The deficit group lost about 2.94 kg of fat (roughly 6.5 pounds) and gained about 1.04 kg of muscle (about 2.3 pounds). The isocaloric group lost about 1.41 kg of fat (about 3.1 pounds) and gained 0.97 kg of muscle (about 2.1 pounds). The control group had no significant changes. The absolute difference in fat loss between the deficit and isocaloric groups was about 1.53 kg (about 3.4 pounds).
This randomized controlled trial compared two high-protein nutritional protocols (isocaloric and moderate energy deficit) combined with a structured resistance training program to a control condition without dietary supervision, to assess effects on body recomposition (simultaneous fat loss and lean mass gain) in resistance-trained individuals.
Both the isocaloric (ISO) and moderate energy deficit (DEF) high-protein diets (2.5 g/kg/day) combined with 10 weeks of resistance training led to significant increases in fat-free mass (FFM) and reductions in fat mass (FM), while the control group showed no meaningful changes. The DEF group lost about twice as much fat mass as the ISO group (absolute reduction of 2.94 kg vs 1.41 kg), while FFM gains were similar (1.04 kg vs 0.97 kg). These findings suggest that body recomposition is possible with high protein intake and resistance training even without a caloric surplus, challenging the traditional energy balance model.
Methods Used
Thirty resistance-trained participants (4 women, 26 men; mean age 23.0 ± 3.4 years) were randomized into three groups: isocaloric diet (ISO, n=10), energy deficit diet (DEF, n=10, -250 kcal/day), and control (CG, n=10, no dietary supervision). All groups performed the same 4-day/week resistance training program for 10 weeks. Both intervention groups consumed 2.5 g/kg/day of protein with different total calories. Body composition was assessed by dual-energy X-ray absorptiometry (DXA) at baseline and post-study.
Main Finding
The DEF group achieved an absolute reduction in fat mass of 2.94 kg (p<0.001) and an increase in fat-free mass of 1.04 kg (p=0.009). The ISO group showed a smaller, non-significant fat mass reduction of 1.41 kg (p=0.051) and a significant FFM increase of 0.97 kg (p<0.001). The control group showed no significant changes. The Time×Group interaction was significant for FFM (p=0.034) and FFM adjusted for fat-free adipose tissue (p=0.006), but not for fat mass. Thus, both high-protein diets with resistance training promoted body recomposition, with the deficit group losing about twice as much fat (absolute difference of 1.53 kg) while gaining similar lean mass.
Confidence Level
Moderate. This is a randomized controlled trial with a small sample size (n=10 per group) and short duration (10 weeks). Dietary intake was not quantified, so adherence to prescribed energy and macronutrient targets cannot be confirmed. The sample was predominantly male and relatively young, limiting generalizability. However, the use of DXA and supervised training adds reliability.
Study Flags
Red Flags
- •Small sample size (n=10 per group) limits statistical power and generalizability
- •Dietary intake was not quantified; adherence to prescribed energy and macronutrient targets cannot be confirmed
- •Short duration (10 weeks) and predominantly male sample (26 men, 4 women) may limit applicability to other populations
Surprising Findings
Body recomposition is possible even without a calorie surplus.
Conventional wisdom says you need a surplus to build muscle and a deficit to lose fat. This study shows both can happen simultaneously with high protein and training.
Practical Takeaways
Consume around 2.5 g of protein per kg of body weight daily if you're resistance training and want to recompose your body.
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 568 / 100
Probability of being correct
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Human RCT
Subject
Moderate probability
on the GRADE evidence scale
This study is like a science experiment where people were randomly put into groups to try different diets. Because it's a randomized experiment, we can say the diet caused the changes, but we need to be careful because the study was small and not everyone knew which group they were in. So we can say the diet might cause changes, but we're not 100% sure.
Strengths
- Randomized controlled design
- Supervised resistance training
- Use of DXA for body composition
Weaknesses
- Small sample size (n=30)
- Lack of blinding
- Dietary adherence not measured
Methodology
Evidence Keywords
Statistical Reporting
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Researchers tested two diets with lots of protein (2.5 grams per kilogram of body weight) plus weight training for 10 weeks. One group ate enough calories to stay the same weight, another ate 250 calories less per day, and a third group just trained without diet advice. Both diet groups gained muscle and lost fat, but the group eating fewer calories lost more fat. The group without diet advice didn't change.
Research results
The deficit group lost about 2.94 kg (6.5 pounds) of fat and gained about 1.04 kg (2.3 pounds) of muscle. The isocaloric group lost about 1.41 kg (3.1 pounds) of fat and gained about 0.97 kg (2.1 pounds) of muscle. The control group had no significant changes.
What this means - more context
These are absolute changes over 10 weeks. The deficit group lost about 2.94 kg of fat (roughly 6.5 pounds) and gained about 1.04 kg of muscle (about 2.3 pounds). The isocaloric group lost about 1.41 kg of fat (about 3.1 pounds) and gained 0.97 kg of muscle (about 2.1 pounds). The control group had no significant changes. The absolute difference in fat loss between the deficit and isocaloric groups was about 1.53 kg (about 3.4 pounds).
This randomized controlled trial compared two high-protein nutritional protocols (isocaloric and moderate energy deficit) combined with a structured resistance training program to a control condition without dietary supervision, to assess effects on body recomposition (simultaneous fat loss and lean mass gain) in resistance-trained individuals.
Both the isocaloric (ISO) and moderate energy deficit (DEF) high-protein diets (2.5 g/kg/day) combined with 10 weeks of resistance training led to significant increases in fat-free mass (FFM) and reductions in fat mass (FM), while the control group showed no meaningful changes. The DEF group lost about twice as much fat mass as the ISO group (absolute reduction of 2.94 kg vs 1.41 kg), while FFM gains were similar (1.04 kg vs 0.97 kg). These findings suggest that body recomposition is possible with high protein intake and resistance training even without a caloric surplus, challenging the traditional energy balance model.
Methods Used
Thirty resistance-trained participants (4 women, 26 men; mean age 23.0 ± 3.4 years) were randomized into three groups: isocaloric diet (ISO, n=10), energy deficit diet (DEF, n=10, -250 kcal/day), and control (CG, n=10, no dietary supervision). All groups performed the same 4-day/week resistance training program for 10 weeks. Both intervention groups consumed 2.5 g/kg/day of protein with different total calories. Body composition was assessed by dual-energy X-ray absorptiometry (DXA) at baseline and post-study.
Main Finding
The DEF group achieved an absolute reduction in fat mass of 2.94 kg (p<0.001) and an increase in fat-free mass of 1.04 kg (p=0.009). The ISO group showed a smaller, non-significant fat mass reduction of 1.41 kg (p=0.051) and a significant FFM increase of 0.97 kg (p<0.001). The control group showed no significant changes. The Time×Group interaction was significant for FFM (p=0.034) and FFM adjusted for fat-free adipose tissue (p=0.006), but not for fat mass. Thus, both high-protein diets with resistance training promoted body recomposition, with the deficit group losing about twice as much fat (absolute difference of 1.53 kg) while gaining similar lean mass.
Confidence Level
Moderate. This is a randomized controlled trial with a small sample size (n=10 per group) and short duration (10 weeks). Dietary intake was not quantified, so adherence to prescribed energy and macronutrient targets cannot be confirmed. The sample was predominantly male and relatively young, limiting generalizability. However, the use of DXA and supervised training adds reliability.
Study Flags
Red Flags
- •Small sample size (n=10 per group) limits statistical power and generalizability
- •Dietary intake was not quantified; adherence to prescribed energy and macronutrient targets cannot be confirmed
- •Short duration (10 weeks) and predominantly male sample (26 men, 4 women) may limit applicability to other populations
Surprising Findings
Body recomposition is possible even without a calorie surplus.
Conventional wisdom says you need a surplus to build muscle and a deficit to lose fat. This study shows both can happen simultaneously with high protein and training.
Practical Takeaways
Consume around 2.5 g of protein per kg of body weight daily if you're resistance training and want to recompose your body.
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 568 / 100
Probability of being correct
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Human RCT
Subject
Moderate probability
on the GRADE evidence scale
This study is like a science experiment where people were randomly put into groups to try different diets. Because it's a randomized experiment, we can say the diet caused the changes, but we need to be careful because the study was small and not everyone knew which group they were in. So we can say the diet might cause changes, but we're not 100% sure.
Strengths
- Randomized controlled design
- Supervised resistance training
- Use of DXA for body composition
Weaknesses
- Small sample size (n=30)
- Lack of blinding
- Dietary adherence not measured
Methodology
Evidence Keywords
Statistical Reporting
Scoring
How strong is this study?
The study was pretty well done because it had a control group and used a special machine to measure body fat and muscle. But it had some problems: only 30 people took part, and we don't know if they actually ate what they were told. So the results are good but not super strong, and we shouldn't trust them completely.
40 / 100
- COI disclosure+40/40
- Data availabilitydata not shared
- Code availabilitycode not shared
60 / 100
- Randomization+20/20
- Blindingblinding unclear
- Control group+15/15
- Sample size (n=30)+2.8/20
- Follow-up+10/10
100 / 100
77 / 100
- P-values+15/15
- Effect size+20/20
- Confidence intervals+15/15
- Pre-registrationnot pre-registered
Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.
Where it sits
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 568 / 100
Probability of being correct
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
This design can establish causation. Although this is an RCT, the small sample size (n=30), lack of blinding, and unquantified dietary adherence limit the strength of causal inferences. The results are specific to this population and may not generalize.
COI Unknown
Could not determine conflict of interest status
No conflicts of interest declared; funding information not provided.
The study text does not include a conflict of interest statement or funding declaration. Author affiliations are not provided.
Standing
Who’s using this study?
The videos and claims on this site that lean on this study, and the researchers who wrote it.
2 videos from Menno Henselmans cite this study, drawing 8 claims from it.
- Unverified · Lacks evidence
Not enough evidence yet — take this with caution.
Evidence - Good evidence
Good evidence supports this claim, with little to contradict it.
Evidence - Very strong evidence
Randomized or controlled trials support this claim, alongside consistent supporting evidence.
Evidence - Unverified · Lacks evidence
Not enough evidence yet — take this with caution.
Evidence - Indication only
Weak evidence — fewer than 20 studies, so treat this as a starting point, not a fact.
Evidence
- Contradicted
Evidence contradicts this claim.
Evidence