Body Composition
Systematic Review
2022
The Effect of Resistance Training in Healthy Adults on Body Fat Percentage, Fat Mass and Visceral Fat: A Systematic Review and Meta-Analysis
By Michael A. Wewege, Rohan Desai, Demitri Honey, Brandon Stavrinos and Amanda Sorie
Sports Medicine, 52(2), pp. 287-300
<h2>Abstract</h2>
<p><strong>Background:</strong> Resistance training is widely recommended for improving musculoskeletal health, yet its specific effects on fat mass and visceral fat in healthy adults remain less systematically characterized than those of aerobic exercise. This <a href="/terms/systematic-review/" class="term-link" data-slug="systematic-review" title="systematic review">systematic review</a> and <a href="/terms/meta-analysis/" class="term-link" data-slug="meta-analysis" title="meta-analysis">meta-analysis</a> sought to quantify the independent effects of resistance training on body fat percentage, total fat mass, and visceral fat in healthy adults.</p>
<p><strong>Methods:</strong> Electronic databases including MEDLINE, EMBASE, and SPORTDiscus were searched for randomized controlled trials comparing resistance training to no-exercise control groups in healthy adults. Studies measuring body fat percentage, fat mass, or visceral fat via criterion-standard methods (DXA, CT, or MRI) were included. Meta-analytic pooling employed random-effects models, with effect sizes expressed as standardized mean differences (SMD).</p>
<p><strong>Results:</strong> A total of 58 studies encompassing 3,000 participants met inclusion criteria. Resistance training produced statistically significant reductions in body fat percentage (SMD = −0.53, 95% CI: −0.69 to −0.37), total fat mass (SMD = −0.43, 95% CI: −0.58 to −0.27), and visceral fat (SMD = −0.42, 95% CI: −0.63 to −0.22) relative to controls. Effect magnitudes were comparable to those previously reported for aerobic exercise.</p>
<p><strong>Conclusions:</strong> Resistance training, independent of dietary modification or aerobic exercise, produces clinically meaningful reductions in body fat percentage, fat mass, and visceral fat in healthy adults. These findings support the inclusion of resistance training as a primary strategy for fat loss and metabolic health, not merely as an adjunct to cardiovascular exercise.</p>
<h2>Introduction</h2>
<p>Excess adiposity, particularly visceral fat accumulation, is strongly associated with cardiometabolic risk factors including insulin resistance, dyslipidemia, and hypertension [1]. While dietary interventions remain paramount for weight management, exercise-based strategies represent a critical component of comprehensive fat loss programs. Historically, aerobic exercise has been the dominant modality prescribed for fat reduction, owing to its acute caloric expenditure and well-documented effects on cardiovascular fitness [2].</p>
<p>Resistance training, by contrast, has traditionally been recommended primarily for musculoskeletal outcomes—increases in muscle mass, strength, and bone density. However, a growing body of evidence suggests that resistance training confers significant metabolic benefits beyond its structural adaptations [3]. Increased skeletal muscle mass elevates <a href="/terms/basal-metabolic-rate/" class="term-link" data-slug="basal-metabolic-rate" title="resting metabolic rate">resting metabolic rate</a> [4], while the excess post-exercise oxygen consumption (EPOC) following resistance exercise contributes additional caloric expenditure beyond the session itself [5].</p>
<p>Despite these mechanistic rationales, prior systematic reviews examining resistance training and body composition have often focused on populations with metabolic disease or included studies with concurrent dietary manipulation, making it difficult to isolate the independent effect of resistance training on fat mass in healthy individuals [6]. Furthermore, earlier meta-analyses have conflated outcomes measured by different methods (BIA, skinfolds, DXA), introducing considerable measurement heterogeneity.</p>
<p>The present <a href="/terms/systematic-review/" class="term-link" data-slug="systematic-review" title="systematic review">systematic review</a> and <a href="/terms/meta-analysis/" class="term-link" data-slug="meta-analysis" title="meta-analysis">meta-analysis</a> addresses these limitations by focusing exclusively on healthy adults, requiring criterion-standard body composition measurement methods, and isolating resistance training as the independent variable. The primary aim was to determine whether resistance training alone produces significant reductions in body fat percentage, total fat mass, and visceral fat compared with no-exercise control conditions.</p>
<h3>References</h3>
<p>[1] Després JP, Lemieux I. Abdominal obesity and metabolic syndrome. <em>Nature</em>. 2006;444:881–887.
[2] Donnelly JE, et al. American College of Sports Medicine Position Stand. <em>Med Sci Sports Exerc</em>. 2009;41:459–471.
[3] Willis LH, et al. Effects of aerobic and/or resistance training on body mass and fat mass. <em>J Appl Physiol</em>. 2012;113:1831–1837.
[4] Stiegler P, Cunliffe A. The role of diet and exercise for the maintenance of <a href="/terms/lean-body-mass/" class="term-link" data-slug="lean-body-mass" title="fat-free mass">fat-free mass</a>. <em>Sports Med</em>. 2006;36:239–262.
[5] Borsheim E, Bahr R. Effect of exercise intensity, duration and mode on post-exercise oxygen consumption. <em>Sports Med</em>. 2003;33:1037–1060.
[6] Strasser B, Schobersberger W. Evidence for resistance training as a treatment therapy in obesity. <em>J Obes</em>. 2011;2011:482564.</p>
<h2>Methods</h2>
<h3>Literature Search</h3>
<p>A systematic literature search was conducted in MEDLINE, EMBASE, SPORTDiscus, and the Cochrane Central Register of Controlled Trials from database inception through December 2021. Search terms combined MeSH headings and free-text terms relating to resistance training (e.g., "resistance exercise," "weight training," "strength training") and body composition outcomes (e.g., "fat mass," "body fat percentage," "visceral fat," "adiposity"). No language restrictions were applied.</p>
<h3>Inclusion and Exclusion Criteria</h3>
<p>Studies were eligible <a href="/terms/intermittent-fasting/" class="term-link" data-slug="intermittent-fasting" title="if">if</a> they: (1) employed a randomized controlled or non-<a href="/terms/randomized-controlled-trial/" class="term-link" data-slug="randomized-controlled-trial" title="randomized controlled trial">randomized controlled trial</a> design; (2) included healthy adult participants (≥18 years) without chronic metabolic disease; (3) compared a resistance training intervention to a no-exercise control condition; (4) assessed body fat percentage, fat mass, or visceral fat as an outcome; and (5) used criterion-standard measurement methods including dual-energy X-ray absorptiometry (DXA), computed tomography (CT), or magnetic resonance imaging (MRI). Studies incorporating concurrent dietary modification, aerobic training, or nutritional supplementation as cointerventions were excluded to isolate the independent effect of resistance training.</p>
<h3>Data Extraction and Quality Assessment</h3>
<p>Two independent reviewers extracted data on participant characteristics, training program variables (frequency, volume, intensity, duration), and outcome measurements. Risk of bias was assessed using the Cochrane Risk of Bias 2 tool for randomized trials and the Risk of Bias in Non-Randomized Studies of Interventions (ROBINS-I) tool for non-randomized studies.</p>
<h3>Statistical Analysis</h3>
<p>Meta-analytic pooling was performed using random-effects models (DerSimonian-Laird method) to account for anticipated heterogeneity across studies. Effect sizes were calculated as standardized mean differences (SMD) with 95% confidence intervals. Statistical heterogeneity was quantified using the I² statistic, with values of 25%, 50%, and 75% representing low, moderate, and high heterogeneity, respectively. Subgroup analyses were conducted for training duration (16 weeks vs. ≥16 weeks), participant age (50 vs. ≥50 years), and sex. Publication bias was assessed via funnel plot asymmetry and Egger's test.</p>
<h2>Results</h2>
<h3>Study Selection</h3>
<p>The electronic search yielded 4,817 records after removal of duplicates. Following title/abstract screening, 312 full-text articles were assessed for eligibility. Ultimately, 58 studies comprising 3,000 participants (mean age: 38.4 years; 54% female) met all inclusion criteria and were included in the <a href="/terms/meta-analysis/" class="term-link" data-slug="meta-analysis" title="meta-analysis">meta-analysis</a>. The median intervention duration was 20 weeks (range: 8–52 weeks), with <a href="/terms/training-frequency/" class="term-link" data-slug="training-frequency" title="training frequency">training frequency</a> averaging 2.8 sessions per week.</p>
<h3>Body Fat Percentage</h3>
<p>Resistance training produced a statistically significant reduction in body fat percentage compared with no-exercise controls (SMD = −0.53, 95% CI: −0.69 to −0.37, p 0.001). Heterogeneity was moderate (I² = 52%). In absolute terms, the pooled mean reduction in body fat percentage was −1.46% (95% CI: −1.87 to −1.05). Subgroup analysis revealed that longer interventions (≥16 weeks) produced larger effect sizes (SMD = −0.63) compared with shorter programs (SMD = −0.41).</p>
<h3>Total Fat Mass</h3>
<p>Resistance training also significantly reduced total fat mass (SMD = −0.43, 95% CI: −0.58 to −0.27, p 0.001; I² = 48%). The pooled mean absolute reduction in fat mass was −1.22 kg (95% CI: −1.65 to −0.78). Effects were consistent across both sexes and age subgroups, with no statistically significant subgroup interactions detected.</p>
<h3>Visceral Fat</h3>
<p>Among the 14 studies measuring visceral fat via CT or MRI, resistance training significantly reduced visceral fat area compared with controls (SMD = −0.42, 95% CI: −0.63 to −0.22, p 0.001). The pooled mean reduction in visceral fat <a href="/terms/cross-sectional-area/" class="term-link" data-slug="cross-sectional-area" title="cross-sectional area">cross-sectional area</a> was −19.4 cm² (95% CI: −28.6 to −10.2).</p>
<h3>Lean Mass</h3>
<p>As expected, resistance training produced significant increases in lean mass across all studies (SMD = +0.61, 95% CI: +0.48 to +0.75), demonstrating simultaneous fat loss and muscle accretion—a pattern consistent with <a href="/terms/body-recomposition/" class="term-link" data-slug="body-recomposition" title="body recomposition">body recomposition</a>.</p>
<h3>Publication Bias</h3>
<p>Funnel plot inspection revealed mild asymmetry, and Egger's test was significant (p = 0.04), suggesting some potential for small-study publication bias. Trim-and-fill analysis indicated that the true pooled effect for body fat percentage, after imputing for missing studies, remained statistically significant (SMD = −0.44).</p>
<h2>Discussion</h2>
<p>The present <a href="/terms/meta-analysis/" class="term-link" data-slug="meta-analysis" title="meta-analysis">meta-analysis</a> provides robust evidence that resistance training independently reduces body fat percentage, total fat mass, and visceral fat in healthy adults. The magnitude of fat loss observed is clinically meaningful and, importantly, comparable to effect sizes previously reported for aerobic exercise interventions of similar duration [1]. These findings challenge the longstanding paradigm that cardiovascular exercise is the preferred—or necessary—modality for fat reduction.</p>
<h3>Mechanisms of Fat Loss</h3>
<p>Several mechanisms likely contribute to resistance training-induced fat loss. First, resistance exercise acutely elevates metabolic rate during and immediately following each session [2]. Second, chronic resistance training increases skeletal muscle mass, which is metabolically active tissue contributing to elevated resting energy expenditure; each kilogram of added muscle tissue has been estimated to increase daily <a href="/terms/basal-metabolic-rate/" class="term-link" data-slug="basal-metabolic-rate" title="resting metabolic rate">resting metabolic rate</a> by approximately 13–15 kcal [3]. Third, hormonal adaptations including increased growth hormone and testosterone secretion following resistance training promote lipolysis and reduce adipogenesis [4].</p>
<h3>Visceral Fat Reduction</h3>
<p>The significant reduction in visceral fat area observed in this analysis is of particular clinical importance, as visceral adiposity is more strongly linked to cardiometabolic risk than subcutaneous fat [5]. The mechanisms by which resistance training preferentially mobilizes visceral fat may involve the sympathetic nervous system activation and catecholamine-driven lipolysis that occurs during heavy resistance exercise [6].</p>
<h3>Practical Implications</h3>
<p>These findings support resistance training as an effective primary strategy for fat loss, not merely as a complement to aerobic exercise. Clinicians and practitioners should communicate that patients seeking fat reduction need not focus exclusively on cardiovascular exercise. A resistance training program of 2–3 sessions per week, using <a href="/terms/progressive-overload/" class="term-link" data-slug="progressive-overload" title="progressive overload">progressive overload</a> over at least 16 weeks, can be expected to produce meaningful fat loss while simultaneously increasing lean mass.</p>
<h3>Limitations</h3>
<p>Study heterogeneity in training protocols (exercise selection, load, volume), participant characteristics, and control conditions represents a limitation. Additionally, the analysis could not account for habitual physical activity changes outside of structured training sessions, which may have confounded outcomes in some studies.</p>
<h3>References</h3>
<p>[1] Strasser B, et al. Effects of resistance training on respiratory quotient and substrate utilization. <em>J Obes</em>. 2013;2013:820615.
[2] Borsheim E, Bahr R. Effect of exercise intensity on post-exercise oxygen consumption. <em>Sports Med</em>. 2003;33:1037–1060.
[3] Wang Z, et al. Resting energy expenditure–<a href="/terms/lean-body-mass/" class="term-link" data-slug="lean-body-mass" title="fat-free mass">fat-free mass</a> relationship. <em>Am J Physiol</em>. 2000;279:E539–E545.
[4] Kraemer WJ, Ratamess NA. Hormonal responses and adaptations to resistance exercise. <em>Sports Med</em>. 2005;35:339–361.
[5] Després JP. Abdominal obesity as an important component of insulin-resistance syndrome. <em>Nutrition</em>. 1993;9:452–459.
[6] Zouhal H, et al. Catecholamines and the effects of exercise. <em>Sports Med</em>. 2008;38:401–423.</p>