Dry Lean Mass Meaning: What the Body-Composition Report Line Shows

Dry lean mass is the part of your body weight left after fat and water are set aside: mostly protein and bone mineral. The term appears on result sheets from InBody, a maker of body-composition analyzers, which describes body weight as body fat mass plus lean body mass, and lean body mass as dry lean mass plus total body water. [1] The company defines dry lean mass as the weight of the protein and the bone mineral in your body. [2] In its own formula, lean body mass minus body water equals dry lean mass, which is where the word “dry” comes from. [3] On these reports the number is not weighed directly: the analyzer sends a small electrical current through the body, and prediction equations turn the readings into estimates of body water and fat-free mass. [4] Dry lean mass is therefore an estimate, and it is not a measure of blood pressure, cholesterol, blood sugar or any of the American Heart Association’s measures of cardiovascular health. [5]

This page is general education for adults. It does not interpret anyone’s results and sets no target for body weight, body composition or protein. If you have a pacemaker or another implanted cardiac device, the analyzer maker advises asking your physician before a test; it also does not recommend testing during pregnancy, because the extra water skews the results. [6] If you follow a diet prescribed by your health care team, such as a protein or sodium limit, use the targets they gave you.

Use the food-comparison guide

What each line on the report means

The table separates what the scale weighs from what the software estimates. It follows the terms as one manufacturer defines them; other devices may label or calculate them differently.

A worked example. In a sample result the company published, total body water of 98.1 plus dry lean mass of 35.5 gives lean body mass of 133.6, in the same units. [8] By our calculation, water is about 73% of lean body mass in that example (98.1 ÷ 133.6 = 0.734) and dry lean mass about 27% (35.5 ÷ 133.6 = 0.266). That 73% matches the classic assumption, reviewed in body-composition research, that water makes up about 0.73 of fat-free mass. [9] Because dry lean mass is the smaller part left after subtracting water, it depends on how well the water estimate fits your body.

Why dry lean mass is an estimate, and how much it can move

• Equations are built on groups of people. Bioelectrical impedance works for estimating fat-free mass and body water in people without significant fluid or electrolyte abnormalities, when equations suited to the person’s population, age or condition are used. The method also lacks standardization. [4]
• Hydration is assumed. Prediction equations are specific to the population and the device, and are valid only when hydration is normal. The makeup of fat-free mass also changes with growth, ageing and disease. [7] [9]
• Testing conditions matter. Body position, recent exercise and recent food or fluid can all change the result. [7] The analyzer maker lists disease, nutrition, hydration, medication, jewelry and posture, and recommends keeping testing conditions the same from test to test. [10]
• Studies differ on how much a meal changes the numbers. In 55 healthy adults measured on a foot-to-foot single-frequency device, eating and drinking changed body-fat readings by a median of about 1% in body-fat percentage units, small and within the method’s imprecision. [11] In 32 athletic men measured by a related method called bioimpedance spectroscopy, testing without standardized conditions produced large changes in fat-free mass estimates. [12]
• Compared with DXA scans, results are consistent but shifted. In 67 adults, three InBody models gave highly repeatable results but, compared with DXA (dual-energy X-ray absorptiometry), estimated less body fat and more fat-free mass, with small individual error. [13] In 41 exercise-trained adults over a four-week reduced-calorie period, another model again estimated more fat-free mass than DXA, but the change over four weeks did not differ significantly between the two methods. [14]
• Manufacturer specifications are not accuracy results. The maker lists its InBody 570 as taking 15 impedance measurements across five body segments at three frequencies (5, 50 and 500 kHz). [15] The independent comparisons cited here report fat and fat-free mass; they do not test the dry lean mass line itself.

What dry lean mass cannot tell you about cardiovascular health

The American Heart Association’s Life’s Essential 8 are its key measures for cardiovascular health: eating better, being more active, quitting tobacco, getting healthy sleep, managing weight, controlling cholesterol, managing blood sugar and managing blood pressure. [5] For weight, the association uses body mass index, a measure of weight in relation to height. [5] Dry lean mass is not one of the eight, and a body-composition report does not measure cholesterol, blood sugar or blood pressure.

The company describes a rise in dry lean mass as a much stronger sign of muscle gain than a rise in lean body mass. [3] That is the manufacturer’s interpretation; the independent studies cited on this page did not test it. A single number on the report does not say whether a person is healthy, and this page does not rate dry lean mass values as good or bad. Some report lines carry the maker’s own ranges and advice to consult a physician, such as its extracellular water ratio. [1] If a line on your report is flagged, ask your doctor what it means for you.

Food-comparison guide: protein, sodium and saturated fat per reference amount

Because dry lean mass is mostly protein and bone mineral, people reading the term often look at protein foods next. This guide compares common protein foods at FDA’s reference amounts, so you can see how sodium and saturated fat differ between foods with similar protein. It does not predict any change in dry lean mass, sets no protein target, and is not individual advice.

Method. Values per 100 g come from USDA FoodData Central SR Legacy entries (FDC numbers shown), a historical data set whose final update was in 2018. [16] Each value is multiplied by FDA’s reference amount customarily consumed for that food category; reference amounts reflect what people customarily eat at one time and are not a recommended portion. [17] Percent Daily Values use FDA’s Daily Values of 2,300 mg for sodium and 20 g for saturated fat. [18] All amounts and percentages in the table are our calculation, rounded (protein to 1 g, sodium to 5 mg, saturated fat to 0.5 g). They describe generic reference foods, not any specific product.

Reading the table. FDA’s general guide is that 5% DV or less of a nutrient per serving is low and 20% DV or more is high, and it suggests choosing foods lower in sodium and saturated fat more often. [19] Foods with similar protein can differ widely in sodium. In our calculation, black beans boiled without salt have less than 5 mg per 90 g, while canned black beans have about 500 mg (22% DV) per 130 g. Cooked salmon has about 50 mg per 85 g; smoked salmon has about 370 mg (16% DV) in a smaller 55 g amount. Cheddar has 5.5 g of saturated fat (28% DV) in 30 g. Packaged foods vary by brand and recipe, so check the label on the product you have; to practice, use the food label reading worksheet.

Before you compare two body-composition reports: a checklist

• Implanted cardiac device. If you have a pacemaker, ventricular assist device or another implanted cardiac device, the maker does not recommend testing and advises asking your physician first. [20]
• Pregnancy. The maker does not recommend testing during pregnancy because extra water and growing mass skew the results. [6]
• Same conditions each time. Keep the time of day, recent food and fluid, recent exercise, posture and removed jewelry the same from test to test. [7] [10]
• Same device. Equations differ between devices and populations, so numbers from two different machines are not directly comparable. [7]
• Look at water and dry lean mass together. Dry lean mass is calculated after body water is subtracted, so a shift in the water estimate can show up in it. [3]
• Flagged values. Ask your doctor about any line the report flags; the report is not a substitute for the checks your doctor uses, such as blood pressure, cholesterol and blood sugar. [5]

Common questions

Is dry lean mass the same as muscle?

No. It is the protein in your body, much of it in muscle, plus bone mineral. [2] [3] Skeletal muscle mass is a separate line on the report. [1]

Why did my dry lean mass change between two tests?

The estimate can shift with food, fluid, recent exercise and body position, so a change between two tests may reflect testing conditions rather than a change in your body. [7] [10] A report cannot tell you which it was.

Is a higher dry lean mass better?

This page does not rate dry lean mass values. The number is an estimate, it is not one of the American Heart Association’s cardiovascular health measures, and what it means for you depends on your health and history. [5] Ask your doctor if you have questions about your results.

Does eating more protein raise dry lean mass?

This page cannot say. The food-comparison guide compares foods at reference amounts; it does not predict a change in any body-composition number or set a protein target.

What does “dry” mean in dry lean mass?

It means the water has been taken out of the lean body mass figure: lean body mass minus body water. [3]

If you have an implanted cardiac device, ask your physician before a body-composition test, and testing is not recommended during pregnancy. [20] [6] If you follow a diet prescribed by your health care team, use the targets they gave you rather than the reference amounts in the guide.

Use the food-comparison guide

More food and label tools are listed in Nutrition and practical resources.

Sources and limitations

1. InBody: Results Interpretation (InBody 570, adult). Manufacturer’s explanation of its own result sheet; describes one device family and is not independent research.
2. InBody USA: Body Composition 101: The Beginner’s Guide. Manufacturer blog; defines terms as the company uses them.
3. InBody USA: Unpacking Body Composition Lingo. Manufacturer blog; its statement about muscle growth is the company’s interpretation, not a study result.
4. Kyle UG, et al. Bioelectrical impedance analysis, part I: review of principles and methods. Clinical Nutrition. 2004. A review of methods; it predates current devices and does not evaluate any one model.
5. American Heart Association: Life’s Essential 8. Consumer overview of the association’s cardiovascular health measures; not individual advice.
6. InBody USA support: Who should be excluded from testing on the InBody? Manufacturer support article covering its own devices.
7. Marra M, et al. Assessment of body composition in health and disease using bioelectrical impedance analysis (BIA) and dual energy X-ray absorptiometry (DXA): a critical overview. Contrast Media & Molecular Imaging. 2019. Narrative review; summarizes limits across methods rather than testing a device.
8. InBody USA: Lean Body Mass and Muscle Mass – What’s the Difference? Manufacturer blog, originally dated August 24, 2018; the worked example is one sample result.
9. Wang Z, et al. Hydration of fat-free body mass: review and critique of a classic body-composition constant. American Journal of Clinical Nutrition. 1999. Review of the hydration assumption across mammals; it describes an average, and individuals can differ.
10. InBody USA support: What factors can affect the accuracy of my InBody test results? Manufacturer support article.
11. Androutsos O, et al. Impact of eating and drinking on body composition measurements by bioelectrical impedance. Journal of Human Nutrition and Dietetics. 2015. 55 healthy adults on one foot-to-foot device; may not apply to other devices or groups.
12. Kerr A, et al. Impact of food and fluid intake on technical and biological measurement error in body composition assessment methods in athletes. British Journal of Nutrition. 2017. 32 athletic men; results may not apply to other groups.
13. McLester CN, et al. Reliability and agreement of various InBody body composition analyzers as compared to dual-energy X-ray absorptiometry in healthy men and women. Journal of Clinical Densitometry. 2020. 67 healthy adults; DXA is itself an estimate, used here as the comparison method.
14. Antonio J, et al. Comparison of DXA versus a multi-frequency bioelectrical impedance (InBody 770) device for body composition assessment after a 4-week hypoenergetic diet. Journal of Functional Morphology and Kinesiology. 2019. 41 exercise-trained adults over four weeks; small sample and a specific group.
15. InBody: InBody 570 product page. Manufacturer’s specifications; not an independent accuracy test.
16. U.S. Department of Agriculture, Agricultural Research Service: FoodData Central. SR Legacy values are historical reference data, last updated in 2018, not measurements of a specific item.
17. Electronic Code of Federal Regulations: 21 CFR 101.12, Reference amounts customarily consumed per eating occasion. Labeling regulation; reference amounts are not dietary recommendations.
18. U.S. Food and Drug Administration: Daily Value on the Nutrition and Supplement Facts Labels. Daily Values are label reference amounts, not personal targets.
19. U.S. Food and Drug Administration: How to Understand and Use the Nutrition Facts Label. Consumer guidance based on a 2,000-calorie general guide; not individual dietary advice.
20. InBody USA support: Can you test on the InBody with an implanted cardiac device? Manufacturer support article covering its own devices.