Body Composition
Narrative Review
2020
Can We Build Muscle and Lose Fat at the Same Time? A Systematic Review and Meta-Analysis of Body Recomposition
By Christopher Barakat, Jeremy Pearson, Guillermo Escalante, Bill I. Campbell and Eduardo O. De Souza
Strength and Conditioning Journal, 42(5), pp. 7-21
<h2>Abstract</h2>
<p>The concept of <a href="/terms/body-recomposition/" class="term-link" data-slug="body-recomposition" title="body recomposition">body recomposition</a>—simultaneous increases in muscle mass and decreases in fat mass—has been a subject of considerable debate within exercise science. Traditional models of energy balance suggest that gaining muscle requires a <a href="/terms/caloric-surplus/" class="term-link" data-slug="caloric-surplus" title="caloric surplus">caloric surplus</a> while losing fat requires a <a href="/terms/caloric-deficit/" class="term-link" data-slug="caloric-deficit" title="caloric deficit">caloric deficit</a>, rendering simultaneous recomposition theoretically difficult. However, emerging evidence challenges this binary view.</p>
<p>This review examines the mechanistic and empirical basis for body recomposition across diverse populations. Evidence from both longitudinal resistance training studies and cross-sectional analyses is synthesized to identify the conditions under which simultaneous fat loss and muscle gain are achievable. Key findings indicate that body recomposition is most robustly documented in (1) resistance training-naïve individuals, (2) individuals with elevated body fat, (3) individuals returning from a period of <a href="/terms/detraining/" class="term-link" data-slug="detraining" title="detraining">detraining</a>, and (4) individuals consuming adequate dietary protein (≥1.6 g/kg/day).</p>
<p>Practical strategies are outlined, including protein intake recommendations, resistance training program design, and the role of energy balance manipulation. The review concludes that body recomposition is not only possible but predictable under appropriate training and nutritional conditions, though the rate and magnitude of recomposition decrease substantially as training experience accumulates and body fat approaches low levels.</p>
<h2>Introduction</h2>
<p><a href="/terms/body-recomposition/" class="term-link" data-slug="body-recomposition" title="Body recomposition">Body recomposition</a>—the simultaneous reduction of fat mass and accretion of muscle mass—represents an appealing but contested goal for individuals engaged in resistance training. The prevailing dogma in applied exercise science has long held that muscle gain and fat loss are fundamentally incompatible within the same time period [1]. This view derives from thermodynamic reasoning: <a href="/terms/muscle-protein-synthesis/" class="term-link" data-slug="muscle-protein-synthesis" title="muscle protein synthesis">muscle protein synthesis</a> requires both amino acid precursors and energy, whereas fat oxidation requires a net <a href="/terms/caloric-deficit/" class="term-link" data-slug="caloric-deficit" title="energy deficit">energy deficit</a>. Following this logic, achieving both outcomes simultaneously would appear to necessitate contradictory energy states.</p>
<p>Despite this theoretical tension, practitioners and athletes have long reported observing apparent body recomposition, particularly in individuals new to resistance training. Early empirical observations of novice trainees gaining lean mass without dietary surplus suggested that under certain conditions, substrate partitioning could favor muscle accretion even without a <a href="/terms/caloric-surplus/" class="term-link" data-slug="caloric-surplus" title="<a href="/terms/concentric-contraction/" class="term-link" data-slug="concentric-contraction" title="positive">positive</a> energy balance">positive energy balance</a> [2].</p>
<p>The past two decades have seen substantial methodological improvements in body composition measurement, including greater adoption of dual-energy X-ray absorptiometry (DXA) and ultrasound-based muscle thickness assessment. These tools have enabled more rigorous documentation of concurrent changes in fat mass and lean mass within the same individuals and timeframes [3].</p>
<p>The present review aims to: (1) outline the physiological mechanisms enabling body recomposition; (2) synthesize the empirical evidence across population subgroups; and (3) provide evidence-based practical recommendations for individuals seeking to achieve body recomposition through resistance training and nutritional strategies.</p>
<h3>References</h3>
<p>[1] Phillips SM. A brief review of critical processes in exercise-induced <a href="/terms/muscle-hypertrophy/" class="term-link" data-slug="muscle-hypertrophy" title="muscular hypertrophy">muscular hypertrophy</a>. <em>Sports Med</em>. 2014;44:71–77.
[2] Stokes T, et al. Recent perspectives regarding the role of dietary protein for the promotion of muscle hypertrophy. <em>Nutrients</em>. 2018;10:180.
[3] Barakat C, et al. Body recomposition: can trained individuals build muscle and lose fat at the same time? <em>Strength Cond J</em>. 2020;42:7–21.</p>
Mechanisms of Body Recomposition
<h2>Mechanisms of <a href="/terms/body-recomposition/" class="term-link" data-slug="body-recomposition" title="Body Recomposition">Body Recomposition</a></h2>
<h3>Substrate Partitioning and Energy Flux</h3>
<p>The central mechanism enabling body recomposition is differential substrate partitioning—the preferential routing of energy substrates toward <a href="/terms/muscle-protein-synthesis/" class="term-link" data-slug="muscle-protein-synthesis" title="muscle protein synthesis">muscle protein synthesis</a> rather than adipose tissue storage [1]. Resistance training potently activates the <a href="/terms/mtor/" class="term-link" data-slug="mtor" title="mTORC1">mTORC1</a> signaling pathway, which drives muscle protein synthesis [2]. Critically, this anabolic stimulus can be met, in part, through the oxidation of endogenous fatty acids stored within adipose tissue, effectively allowing fat to "fund" muscle construction even under conditions of neutral or slightly <a href="/terms/caloric-deficit/" class="term-link" data-slug="caloric-deficit" title="<a href="/terms/eccentric-contraction/" class="term-link" data-slug="eccentric-contraction" title="negative">negative</a> energy balance">negative energy balance</a>.</p>
<h3>The Role of Protein Synthesis Rate</h3>
<p>Muscle protein synthesis rates following resistance exercise remain elevated for 24–48 hours post-training [3]. During this window, dietary protein provides amino acids for anabolic processes while the body's energy demands are met through a combination of dietary carbohydrate, dietary fat, and stored adipose-derived free fatty acids. When dietary protein is sufficient but total caloric intake is modestly restricted, the net result may be simultaneous lean mass accretion and fat mass reduction [4].</p>
<h3>Hormonal Contributions</h3>
<p>Resistance training acutely elevates anabolic hormones including testosterone, growth hormone, and insulin-like growth factor-1 (<a href="/terms/igf-1/" class="term-link" data-slug="igf-1" title="IGF-1">IGF-1</a>), while chronically improving insulin sensitivity [5]. Enhanced insulin sensitivity facilitates glucose uptake into muscle rather than storage in adipose tissue, supporting a metabolic environment conducive to recomposition. Additionally, elevated resting catecholamine tone following training promotes lipolysis, further supporting fat oxidation as an energy substrate.</p>
<h3>The "Newbie Gains" Phenomenon</h3>
<p>Untrained individuals exhibit a disproportionate anabolic response to initial resistance training stimuli, often termed "newbie gains" [6]. This accelerated muscle protein synthesis, combined with substantial hormonal and neuromuscular adaptations, enables fat loss and muscle gain to proceed in <a href="/terms/squat-depth/" class="term-link" data-slug="squat-depth" title="parallel">parallel</a> at rates that are rarely replicated in experienced trainees.</p>
<h3>References</h3>
<p>[1] Hall KD. Body composition and energy expenditure. <em>Curr Opin Clin Nutr Metab Care</em>. 2011;14:341–348.
[2] Laplante M, Sabatini DM. mTOR signaling in growth control and disease. <em>Cell</em>. 2012;149:274–293.
[3] Phillips SM, et al. Mixed muscle protein synthesis and breakdown after resistance exercise. <em>Am J Physiol</em>. 1997;273:E99–E107.
[4] Barakat C, et al. Body recomposition. <em>Strength Cond J</em>. 2020;42:7–21.
[5] Kraemer WJ, Ratamess NA. Hormonal responses to resistance exercise. <em>Sports Med</em>. 2005;35:339–361.
[6] Damas F, et al. Early-resistance training-induced increases in muscle <a href="/terms/cross-sectional-area/" class="term-link" data-slug="cross-sectional-area" title="cross-sectional area">cross-sectional area</a>. <em>J Appl Physiol</em>. 2016;121:1378–1388.</p>
<h2>Population-Specific Considerations</h2>
<h3>Resistance Training Novices</h3>
<p>The strongest and most consistently documented evidence for <a href="/terms/body-recomposition/" class="term-link" data-slug="body-recomposition" title="body recomposition">body recomposition</a> exists in individuals new to structured resistance training [1]. Multiple studies have demonstrated simultaneous increases in lean mass and decreases in fat mass in untrained individuals over 8–16 week programs, even when caloric intake is not specifically manipulated to create a surplus. The magnitude of these changes is often substantial, with novices gaining 1–3 kg of lean mass while losing 1–2 kg of fat mass within the same intervention period [2].</p>
<h3>Individuals with Elevated Body Fat</h3>
<p>Individuals with obesity or high body fat percentage represent another group for whom recomposition is particularly achievable. Greater adipose reserves provide an abundant substrate for energy supply during periods of <a href="/terms/muscle-protein-synthesis/" class="term-link" data-slug="muscle-protein-synthesis" title="muscle protein synthesis">muscle protein synthesis</a> [3]. Furthermore, higher initial insulin resistance means that even modest improvements in insulin sensitivity—driven by resistance training—produce outsized metabolic benefits. Several studies in overweight and obese populations have documented robust recomposition even with only modest caloric deficits.</p>
<h3><a href="/terms/detraining/" class="term-link" data-slug="detraining" title="Detraining">Detraining</a> and Return to Training</h3>
<p>Athletes or trained individuals returning from an extended period of detraining (<a href="/terms/muscle-memory/" class="term-link" data-slug="muscle-memory" title="muscle memory">muscle memory</a> phenomenon) demonstrate rapid recomposition potential upon resuming training [4]. The epigenetic changes in <a href="/terms/myonuclei/" class="term-link" data-slug="myonuclei" title="myonuclei">myonuclei</a> that persist through detraining periods allow accelerated re-synthesis of contractile proteins when training resumes, enabling muscle re-accretion to outpace any dietary deficit.</p>
<h3>Trained and Lean Individuals</h3>
<p>For experienced resistance-trained individuals at low body fat percentages, simultaneous recomposition becomes progressively more difficult [5]. The anabolic response to training stimuli is blunted relative to novices, and reduced adipose reserves limit the capacity for endogenous energy supply to muscle protein synthesis. In this population, recomposition is still achievable but typically requires very precise nutritional strategies—maintenance or slightly above-maintenance calories, high protein intake (≥2.2 g/kg), and strategic energy <a href="/terms/periodization/" class="term-link" data-slug="periodization" title="periodization">periodization</a>—with a much slower rate of change.</p>
<h3>References</h3>
<p>[1] Morton RW, et al. Neither load nor systemic hormones determine <a href="/terms/muscle-hypertrophy/" class="term-link" data-slug="muscle-hypertrophy" title="hypertrophy">hypertrophy</a>. <em>J Appl Physiol</em>. 2016;121:129–138.
[2] Barakat C, et al. Body recomposition in resistance-trained individuals. <em>Strength Cond J</em>. 2020;42:7–21.
[3] Villareal DT, et al. Effect of weight loss and exercise on frailty in obese older adults. <em>N Engl J Med</em>. 2011;364:1218–1229.
[4] Egner IM, et al. A cellular memory mechanism aids overload hypertrophy. <em>J Physiol</em>. 2013;591:3739–3749.
[5] Roberts BM, et al. Nutritional recommendations for physique athletes. <em>J Hum Kinet</em>. 2020;71:79–108.</p>
<h2>Practical Strategies</h2>
<h3>Protein Intake</h3>
<p>Adequate dietary protein is arguably the single most critical nutritional variable for <a href="/terms/body-recomposition/" class="term-link" data-slug="body-recomposition" title="body recomposition">body recomposition</a>. A minimum intake of 1.6 g/kg/day of body weight is supported by meta-analytic evidence as necessary to maximize <a href="/terms/muscle-protein-synthesis/" class="term-link" data-slug="muscle-protein-synthesis" title="muscle protein synthesis">muscle protein synthesis</a> in the context of resistance training [1]. For individuals in a <a href="/terms/caloric-deficit/" class="term-link" data-slug="caloric-deficit" title="caloric deficit">caloric deficit</a>, higher protein intakes of 2.2–3.1 g/kg/day provide an additional protective effect against lean mass catabolism [2]. Protein should be distributed across 3–5 meals or feeding occasions, with each meal providing 0.4–0.6 g/kg to maximize the <a href="/terms/leucine/" class="term-link" data-slug="leucine" title="leucine">leucine</a>-driven anabolic response.</p>
<h3>Energy Balance Management</h3>
<p>For novices and individuals with elevated body fat, body recomposition can occur across a range of energy balance states, from modest surplus to moderate deficit [3]. A practical strategy is to target near-maintenance caloric intake (±200–300 kcal/day), relying on the acute energy demands of resistance training and elevated post-exercise fat oxidation to drive any necessary deficit. Larger caloric deficits (500 kcal/day) increase the risk of lean mass catabolism and should be avoided unless substantial fat loss is the primary priority.</p>
<h3>Resistance Training Design</h3>
<p>A well-structured resistance training program forms the foundation of any recomposition protocol. Key evidence-based principles include <a href="/terms/progressive-overload/" class="term-link" data-slug="progressive-overload" title="progressive overload">progressive overload</a> (increasing training stimulus over time), adequate volume (10–20 sets per muscle group per week), and sufficient frequency (each muscle group trained 2–3 times per week) [4]. Compound multi-joint exercises provide the greatest anabolic stimulus and energy expenditure per unit time.</p>
<h3>Refeed Periods and Diet Breaks</h3>
<p>Strategic refeed days (short-term caloric and carbohydrate increases to maintenance or above) may attenuate adaptive thermogenesis and preserve anabolic hormone levels during prolonged body recomposition phases [5]. Evidence for diet breaks (2-week periods at maintenance calories) suggests they may improve adherence and body composition outcomes in longer-term interventions.</p>
<h3>Measurement and Monitoring</h3>
<p>Given that scale weight may remain relatively stable during recomposition even as fat is lost and muscle is gained, individuals should monitor body composition through regular DXA scans, circumference measurements, and progress photographs rather than relying on bodyweight alone as an outcome metric.</p>
<h3>References</h3>
<p>[1] Morton RW, et al. A <a href="/terms/systematic-review/" class="term-link" data-slug="systematic-review" title="systematic review">systematic review</a>, <a href="/terms/meta-analysis/" class="term-link" data-slug="meta-analysis" title="meta-analysis">meta-analysis</a> and meta-regression of <a href="/terms/protein-supplementation/" class="term-link" data-slug="protein-supplementation" title="protein supplementation">protein supplementation</a> and <a href="/terms/muscle-hypertrophy/" class="term-link" data-slug="muscle-hypertrophy" title="hypertrophy">hypertrophy</a>. <em>Br J Sports Med</em>. 2018;52:376–384.
[2] Helms ER, et al. A systematic review of dietary protein during caloric restriction. <em>Int J Sport Nutr Exerc Metab</em>. 2014;24:198–214.
[3] Barakat C, et al. Body recomposition. <em>Strength Cond J</em>. 2020;42:7–21.
[4] Schoenfeld BJ. The mechanisms of muscle hypertrophy and their application to resistance training. <em>J Strength Cond Res</em>. 2010;24:2857–2872.
[5] Byrne NM, et al. Intermittent energy restriction improves weight loss efficiency. <em>Int J Obes</em>. 2018;42:129–138.</p>