Where your DNA places you among other people, and the studies behind it.
Not tailored to your result, and not medical advice
Do Regular Resistance Training: Resistance training is the strongest behavioral lever on lean mass. A meta-analysis of 114 randomised trials in 4,184 people with overweight or obesity found resistance training alone increased lean mass by about 0.8 kg (95% CI 0.6 to 1.0 kg) versus untrained controls. The gains were not uniform: young adults averaged 1.4 kg and middle-aged adults 0.3 kg, and the pooled effect in men on their own did not reach statistical significance. When resistance training was combined with calorie restriction, lean mass did not change measurably (about -0.2 kg, p = 0.73), so training appears to hold lean tissue roughly steady during weight loss. Obesity Reviews (PMC)
Eat Enough Daily Protein: Total daily protein intake adds to resistance training, but mainly alongside it. A meta-analysis of 74 randomised trials found extra protein produced small additional gains in lean body mass in people who were also resistance training (standardised effect 0.22, 95% CI 0.14 to 0.30), with benefit appearing at intakes of roughly 1.6 g of protein per kg of body weight per day in adults under 65, and around 1.2 to 1.6 g/kg/day in those 65 and over. Without resistance exercise, the effect on lean body mass was small and not statistically significant. Ordinary foods carry this: dairy, eggs, fish, poultry, meat, soy, beans and lentils. Journal of Cachexia, Sarcopenia and Muscle (PMC)
Avoid Steep Calorie Deficits: A meta-analysis pooled trials of resistance training performed under an energy deficit and found lean mass gains were impaired compared with training while eating enough (effect size -0.57, p = 0.02). The accompanying meta-regression put the point at which lean mass gains stopped at an energy deficit of roughly 500 kcal a day. Strength gains were comparable in both conditions (effect size -0.31, p = 0.28), so getting stronger during a diet is not evidence that lean tissue is being preserved. Scandinavian Journal of Medicine & Science in Sports (PubMed)
Break Up Long Inactive Stretches: Short spells of ordinary inactivity move lean mass measurably. In the step-reduction studies collected in this review, young adults who cut to under 1,500 steps a day for two weeks lost leg lean mass, with reported losses of about 0.5 kg in one trial that held energy intake steady and 2.8% of leg lean mass in another. Older adults were studied under similar reductions, and recovery appears less complete with age: muscle protein synthesis rates had not returned to baseline after two weeks back at habitual activity. Illness, injury and desk-bound weeks are the everyday version of this model. Frontiers in Nutrition (PMC)
Protect Sleep While Losing Weight: In a crossover trial, 10 overweight adults completed two 14-day rounds of identical calorie restriction, once with 8.5 hours in bed a night and once with 5.5. Total weight lost was similar, but the composition shifted: fat loss fell from 1.4 kg to 0.6 kg while fat-free mass loss rose from 1.5 kg to 2.4 kg. This is a small, short study of 10 people, so the exact figures should be read loosely, but it is one of the few designs that isolates sleep while holding food intake constant. Annals of Internal Medicine (PMC)
How much of this is genetic?
Genetics explains 50% of why people differ in this trait. The rest is environment, daily habits and chance.
Heritability estimate: Twin and family studies estimate heritability of lean body mass at roughly 50 to 80 percent; Zillikens MC, et al. Nature Communications, 2017
Background and further reading
Lean body mass (also called fat-free mass) is everything in your body that is not stored fat: skeletal muscle, bone, connective tissue, organs, and body water. Skeletal muscle makes up the largest and most variable component. Lean mass is closely tied to physical strength, resting metabolic rate, glucose handling, and physical resilience, and it tends to decline gradually from mid-life onward in a process called sarcopenia. Because it is measured separately from fat mass (typically by DXA or bioimpedance), two people of identical body weight can have very different amounts of lean tissue.
Genetic Basis: Twin and family studies place the heritability of lean body mass at roughly 50 to 80 percent, meaning a substantial share of the person-to-person variation is inherited, though estimates vary with age and how lean mass is measured. Like height, it is highly polygenic, shaped by many common variants each with a small effect rather than a few major genes. A large genome-wide meta-analysis of appendicular and whole-body lean mass identified loci near genes such as HSD17B11, VCAN, ADAMTSL3, IRS1, and FTO, pointing to biology spanning connective tissue, insulin signaling, and body composition. This score aggregates many such variants into a single estimate of genetic tendency.
Environmental Factors: Genetics sets a tendency, but lean mass is strongly modifiable. Resistance and progressive strength training is the most effective way to build and preserve muscle, and adequate dietary protein supports muscle protein synthesis, especially in older adults. Overall energy intake, physical activity level, sleep, and hormones (including testosterone, growth hormone, and estrogen) all influence how much lean tissue you carry. Aging, prolonged inactivity or bed rest, and chronic illness push lean mass down, while consistent training and nutrition can raise it well above what genetics alone would predict.
The published research behind your score, and the variants it draws on.
21 published scores from 5 studies
The lean body mass score combines 21 polygenic scores drawn from 5 published studies.
These traits are influenced by some of the same genes and variants as this one
Height: Adult standing height - one of the most heritable and polygenic human traits.
Body Mass Index: A measure of body weight relative to height, used as a proxy for overall adiposity.
Content updated August 2026.
ReadYourDNA provides educational interpretation of DNA data you already have. It is not diagnostic, not a substitute for professional medical advice, diagnosis, or treatment, and is not intended to diagnose, treat, cure, or prevent any disease. Talk to a clinician before acting on any result.
Raw DNA Data Reports for 23andMe & AncestryDNA · About ReadYourDNA · FAQ · Methodology & Science · Pricing · Support and complaints · Legal & Contact · Health Traits · Pharmacogenomics · Carrier Status · Variant Explorer · The Human Karyotype · Privacy Policy · Terms of Service · Accessibility · Consumer Health Data Privacy · Your Privacy Choices · Editorial Standards · Your Data, Checkable · Sample Report · ReadYourDNA and Promethease compared · What is inside a 23andMe raw data file · What is inside an AncestryDNA raw data file · What a chatbot can and cannot do with your raw DNA file · Where a raw DNA file can still be uploaded in 2026
Written, maintained and operated by Martin Pechhacker, sole proprietor, Vienna, Austria. Trade register GISA 40064420. support@readyourdna.com