Training every muscle group is key because building muscle reduces body fat systemically.
A new review suggests that building muscle reduces body fat more consistently than many people realize. Across 122 studies, researchers found that muscle hypertrophy was repeatedly associated with lower fat mass and better blood sugar markers. The findings provide some of the strongest evidence to date that building muscle reduces body fat across a wide range of populations and interventions.
Key Takeaways on How Building Muscle Reduces Body Fat
- Building muscle was consistently linked to lower body fat across 122 studies.
- Human participants gained an average of 2.7% muscle mass while reducing fat mass by 4.1%.
- Drug-only human studies: muscle mass rose 4.1 ± 2.6% and fat mass fell 8.9 ± 5.0%.
- Blood sugar markers improved alongside muscle growth, although researchers cannot fully separate the effects of exercise from the effects of muscle gain itself.
How Building Muscle Reduces Body Fat
Most people think of muscle as something you build to look better, get stronger, or improve athletic performance. But what if building muscle could also help you lose fat and improve your blood sugar?
The new paper, “Effects of Skeletal Muscle Hypertrophy on Fat Mass and Glucose Homeostasis in Humans and Animals: A Narrative Review with Systematic Literature Search,” by Havers, Held, Schönfelder, Geisler, and Wackerhage, published in Sports Medicine in 2025, takes a broader look (Havers et al., 2025). The authors asked a practical question: when researchers increase skeletal muscle mass, do fat mass and glucose control improve as well?
This research is important because most conversations about fat loss focus on eating fewer calories, doing more cardio, or using weight-loss drugs. Those approaches can work, but many of them come with a downside: they often lead to muscle loss along with fat loss.
Muscle is one of the most metabolically active tissues in the body. Losing it can make it harder to stay strong, maintain performance, and support long-term health. That raises an important question: could building more muscle be one of the most effective ways to improve body composition?
The findings from this review suggest the answer may be yes
Building Muscle Reduces Body Fat: Why This Question Matters
Scientists have known for decades that skeletal muscle plays a major role in regulating blood sugar. In fact, muscle tissue is responsible for most of the glucose removed from the bloodstream after eating (DeFronzo et al., 1985). Simply put, the more muscle you have, the more space your body has to store and use nutrients. Researchers have also observed a similar pattern in animal studies. Mice that naturally grow unusually large amounts of muscle tend to stay leaner and have better blood sugar control than normal mice (McPherron & Lee, 2002).
Interestingly, farmers have used similar principles for years. Certain livestock treatments can shift nutrients away from fat storage and toward muscle growth, resulting in leaner, more muscular animals (Sillence, 2004).
Although these findings are intriguing, most previous research focused on individual studies. Until now, no large review had pulled together evidence from more than one hundred studies to see whether the same pattern appears consistently across different populations, age groups, and interventions.
That is exactly what Havers and colleagues set out to investigate.
What the Study Looked At
Havers et al. (2025) conducted a narrative review with systematic literature search. That distinction matters. The authors conducted a systematic search, but this was not a formal meta-analysis with pooled effect sizes and full heterogeneity testing.
Search Strategy
The authors searched PubMed/MEDLINE, SPORTDiscus, and Scopus on September 17, 2024.
Inclusion Criteria
Studies had to be peer-reviewed and published in English, induce global muscle hypertrophy through resistance training, drugs, or genetic manipulation, and report changes in fat mass and/or glucose-related outcomes.
Total Studies Included
The team included 122 total studies, including 99 human interventions and 23 animal models. More than 2,700 human participants were represented across the included studies featuring durations from 2 weeks to 3 years.
Measurements
Body composition was mainly measured using DEXA (dual-energy X-ray absorptiometry) and BIA (bioelectrical impedance analysis). Glucose outcomes included fasting blood glucose and HbA1c (a marker of average blood sugar over roughly 2–3 months).
Results: Building Muscle Reduces Body Fat Across 122 Studies
The clearest finding from the review was surprisingly consistent.
Across human studies, participants who gained muscle generally lost body fat.
On average:
- Muscle mass increased by 2.7%
- Fat mass decreased by 4.1%
- When the authors split the human studies by intervention type, the pattern held:Drug-only studies: muscle mass +4.1 ± 2.6%, fat mass -8.9 ± 5.0%
Resistance training studies: muscle mass +2.3 ± 1.9%, fat mass -3.0 ± 5.4%
Combined training + drug studies: muscle mass +4.7 ± 1.5%, fat mass -9.6 ± 5.9%
The relationship was statistically significant, meaning it was unlikely to be due to random chance.
In other words, when muscle went up, fat usually went down.
This pattern appeared in:
- Younger adults
- Middle-aged adults
- Older adults
- Lean individuals
- Overweight individuals
- Obese individuals
- Trained lifters
- Beginners
That consistency is one of the most impressive aspects of the review.
Building Muscle Reduces Body Fat: Why It Happens
When researchers looked only at resistance-training studies, participants gained an average of 2.3% muscle mass while reducing body fat by approximately 3%.
That may not sound dramatic at first, but it is important to remember that these changes occurred while participants were building new muscle tissue.
Many people focus entirely on the number on the scale. However, gaining muscle while losing fat can dramatically improve body composition even when body weight changes very little.
The review proposed two main explanations for why this data occurs.
1. Muscle Signaling
Growing muscle may release signaling molecules — often called myokines — that influence fat tissue and glucose metabolism. The review also discussed myostatin suppression as one possible pathway that favors lean tissue over fat storage (Pillon et al., 2020; Guo et al., 2009).
2. Metabolic Steal
Building new muscle tissue requires raw materials. The authors estimate that for every 1 kilogram (2.2 pounds) of new muscle tissue, about 300 grams (0.66 pounds) of metabolites must be pulled from circulation (Havers et al., 2025). In theory, that could leave fewer nutrients available for fat storage.
Practical Applications of Building Muscle Reduces Body Fat
For many lifters, evidence suggests that building muscle reduces body fat and supports long-term metabolic health.
Practically, this paper gives you a strong reason to care about muscle gain and fat loss as connected goals rather than opposite ones.
If your goal is better body composition, three points stand out:
- Do not judge progress by body weight alone. If you gain muscle while losing fat, the scale can understate real progress.
- Resistance training deserves a central place in fat-loss phases. The paper supports the idea that hypertrophy-oriented training is not just for bulking.
- Measure body composition when possible. DEXA, BIA, waist measurements, progress photos, and gym performance tell you more than BMI alone.
For coaches, the most practical message is simple: when a client improves muscle mass during a fat-loss phase, that is not a side note. It may be a major part of why the intervention is working.
Limitations of Research on How Building Muscle Reduces Body Fat
This review has real strengths, but it also has important limitations. First, it was a narrative review, not a formal meta-analysis. That means the quantitative summaries are descriptive and should not be treated like pooled effect sizes with full risk-of-bias analysis.
Second, in human studies, resistance training itself is a major confounder. Exercise increases energy expenditure and improves insulin sensitivity independently of hypertrophy. Isolating the specific effect of muscle gain alone is inherently difficult.
Third, the types of included participants varied widely. That broadens the relevance of the review, but limits how literally you should take any single summary statistic relative to your personal training status.
Bottom Line: Does Building Muscle Reduce Body Fat?
So, does building muscle reduce body fat?
Based on this 122-study review, muscle hypertrophy is consistently associated with lower fat mass across humans and animals, and it is also linked to better blood sugar markers (Havers et al., 2025). That does not mean every mechanism is settled or that causality is perfectly isolated in humans. But it does support a practical conclusion: if you care about body composition and metabolic health, building muscle deserves to be a primary goal rather than an afterthought.
FAQ
Does building muscle reduce body fat?
This review suggests it often does in practice. Muscle hypertrophy was consistently associated with lower fat mass across a large body of studies. In human interventions, average muscle gain of 2.7% was linked to an average fat-mass reduction of 4.1% (Havers et al., 2025).
Does building muscle also improve blood sugar?
Building muscle improves blood sugar is directionally supported by this review, but the clinical version is that hypertrophy is strongly associated with better blood sugar markers. Fasting glucose fell by 5.8% on average, and HbA1c also tended to decrease.
Is muscle hypertrophy and fat loss possible at the same time?
Muscle hypertrophy and fat loss can occur together. This review suggests that pairing is common across many intervention studies. That does not guarantee it will happen rapidly under all conditions, but it does challenge the idea that you must always choose one or the other.
Does muscle gain help with glucose control?
Muscle gain and glucose control appear to move in the same direction in much of the literature reviewed by Havers et al. (2025). Since skeletal muscle is a major site of glucose uptake, that pattern makes biological sense despite the training confounders.
References
DeFronzo, R. A., Gunnarsson, R., Björkman, O., Olsson, M., & Wahren, J. (1985). Effects of insulin on peripheral and splanchnic glucose metabolism in noninsulin-dependent (type II) diabetes mellitus. Journal of Clinical Investigation, 76, 149–155. https://doi.org/10.1172/JCI111938
Guo, T., Jou, W., Chanturiya, T., Portas, J., Gavrilova, O., & McPherron, A. C. (2009). Myostatin inhibition in muscle, but not adipose tissue, decreases fat mass and improves insulin sensitivity. PLoS ONE, 4, e4937. https://doi.org/10.1371/journal.pone.0004937
Havers, T., Held, S., Schönfelder, M., Geisler, S., & Wackerhage, H. (2025). Effects of skeletal muscle hypertrophy on fat mass and glucose homeostasis in humans and animals: a narrative review with systematic literature search. Sports Medicine, 55, 1867–1885. https://doi.org/10.1007/s40279-025-02263-w
Janssen, I., Heymsfield, S. B., Wang, Z. M., & Ross, R. (2000). Skeletal muscle mass and distribution in 468 men and women aged 18–88 yr. Journal of Applied Physiology, 89, 81–88. https://doi.org/10.1152/jappl.2000.89.1.81
Mechanick, J. I., et al. (2024). Strategies for minimizing muscle loss during use of incretin-mimetic drugs for treatment of obesity. Obesity Reviews. https://doi.org/10.1111/obr.13841
McPherron, A. C., & Lee, S.-J. (2002). Suppression of body fat accumulation in myostatin-deficient mice. Journal of Clinical Investigation, 109, 595–601. https://doi.org/10.1172/JCI13562
Pillon, N. J., et al. (2020). Transcriptomic profiling of skeletal muscle adaptations to exercise and inactivity. Nature Communications, 11, 470. https://doi.org/10.1038/s41467-019-13869-w
Sillence, M. N. (2004). Technologies for the control of fat and lean deposition in livestock. Veterinary Journal, 167, 242–257. https://doi.org/10.1016/j.tvjl.2003.10.020
About the Author
Robbie Durand
Robbie Durand is an exercise physiologist and science writer specializing in evidence-based fitness and nutrition research. With over 15 years of experience translating peer-reviewed studies into actionable advice, Robbie helps readers make informed decisions about training, supplementation, and body composition.
