BMR
Basal Metabolic Rate (BMR)
Basal Metabolic Rate estimates the energy your body uses over 24 hours at complete rest for basic life functions; InBody calculates it from fat free mass.
Short answer
BMR from InBody is not a measured metabolism but your fat free mass converted by one equation. Treat it as an orientation baseline and as a reminder that more muscle means higher resting expenditure.
What the value represents
BMR is the energy baseline. It covers breathing, the work of the heart, maintaining body temperature and the activity of organs — what the body does even while you lie still and do nothing.
It is not your total daily expenditure. Energy for movement, ordinary daily activity and digestion is added on top of the basal rate.
InBody does not measure it. The manual itself states that the standard for establishing it is measuring oxygen consumption and carbon dioxide production; InBody instead substitutes your fat free mass into an equation.
In practice this means the BMR on the result sheet is another way of expressing your fat free mass. Knowing the latter, you can work out the number yourself.
- An estimate of resting energy expenditure over 24 hours in kilocalories.
- A restatement of fat free mass, because it is calculated from that and nothing else.
- It does not represent total daily energy expenditure or a recommended daily intake.
How the value is produced
- A calculated value, not a measured one. The manual gives the equation BMR = 21.6 × fat free mass (kg) + 370 and refers to the 1991 work of Cunningham.
- Fat free mass is itself an estimate from bioimpedance, derived from total body water. The uncertainty of the FFM estimate therefore propagates directly into BMR.
- Age, sex and height do not enter the equation. Two people with the same fat free mass receive the same BMR regardless of how else they differ.
- A reference range is shown next to the value on the result sheet. The manual does not publish how it is calculated.
How to read the current value
- Read the number as a restatement of fat free mass rather than independent information about your metabolism.
- The manual states that higher muscle mass means a higher BMR: two people of the same weight but different amounts of muscle will have different basal rates.
- Do not use BMR directly as a daily calorie target. It is a resting baseline, not total expenditure.
- The equation knows nothing of your thyroid, medication, sleep, ambient temperature or whether you have been in a calorie deficit for a long time. Actual resting expenditure can differ from the estimate.
How to read change over time
- In this calculation BMR moves only when fat free mass moves. A difference of tens of kilocalories between two measurements reflects variation in the FFM estimate, typically via hydration.
- A rise in BMR after months of strength training makes sense. A jump between two measurements days apart does not.
- The manual notes that during weight loss the body lowers its actual basal metabolic rate to conserve energy. An equation based on fat free mass cannot capture that adaptation directly — it shows only indirectly, if fat free mass falls too.
General principles: how to read change between measurements →
What to read it with
- Fat free mass (FFM) – the only input to the equation.
- Skeletal Muscle Mass – the main changeable component of fat free mass.
- Weight and fat mass – the context in which the value is interpreted.
- Recommended calorie intake – a different value with a different purpose; do not confuse the two.
- Total body water – the quantity fat free mass is estimated through.
Common misunderstandings
- BMR from InBody is not a measured metabolism. It is the output of an equation with a single input.
- BMR is not your daily calorie requirement. Anyone eating only that much would be eating below their actual expenditure.
- A higher BMR is not automatically better. It is mainly a consequence of having more fat free mass.
- The equation does not use age or sex, even though actual resting expenditure is influenced by both. That is a property of the model used, not a measurement error.
- A change in BMR between two measurements is not evidence of a sped-up or slowed-down metabolism; it reflects only a change in the fat free mass estimate.
What can affect the result short term
- Hydration, food and drink before the measurement, because they shift the fat free mass estimate.
- Training, sauna and showering shortly before the measurement.
- Time of day and the shift of fluid towards the lower half of the body.
- The menstrual cycle, during which fluid retention fluctuates.
- Illness and fever, which change both fluid distribution and actual energy expenditure.
What to do next
The explanation of the value is the same for everyone. Only the suggested step changes — pick whichever fits you.
- If you want to raise BMR, the only route within this calculation runs through increasing fat free mass, that is chiefly muscle.
- To set an intake you also need an estimate of your physical activity on top of BMR. The number alone is not enough.
- During weight reduction, watch muscle mass alongside weight — the manual explicitly says it is better to raise BMR by gaining muscle than by starving.
- If you suspect a hormonal cause of unusual expenditure, the thyroid for instance, that belongs with a doctor. An estimate calculated from fat free mass cannot reveal it.
What the value does not determine
- It is not a measured resting expenditure; the standard for establishing that is indirect calorimetry.
- It does not account for age, sex, hormonal status, medication or adaptation to a calorie deficit.
- It inherits the uncertainty of the bioimpedance fat free mass estimate.
- It is not a recommended daily energy intake.
On terminology
- Basal metabolic rate (BMR) and resting energy expenditure (REE) are used interchangeably in practice but are not the same — they differ in how strictly the conditions of measurement are defined. InBody reports an estimate from the Cunningham equation.
In more depth, with sourcesIn more depth: the Cunningham equation and its limitsExpand the detailed explanation
The manual states that InBody calculates basal metabolic rate as BMR = 21.6 × FFM (kg) + 370, referring to the 1991 work of John J. Cunningham. This is a linear regression derived from population data, whose logic rests on fat free mass being the metabolically active tissue that explains most of the differences in resting expenditure between people. The constant of 370 kcal is the intercept of the regression line, not a physiological quantity; outside the range of data the equation was built on it therefore returns values with no support.
The input to the equation is an estimate. In bioimpedance, fat free mass is derived from total body water assuming a roughly constant water content of lean tissue. An error in the FFM estimate propagates into the result with a coefficient of 21.6: a deviation of one kilogram of fat free mass shifts BMR by roughly 22 kcal. The NIH consensus statement on bioimpedance therefore emphasises standardised measurement conditions, and the ESPEN clinical guidelines name altered fluid distribution as a situation in which body composition estimates are less reliable.
The equation also cannot capture adaptive change. The manual itself states that with reduced energy intake the body lowers its basal metabolic rate. A model whose only input is fat free mass sees that adaptation only when it manifests as a loss of lean mass. In someone in a long-term deficit, actual resting expenditure can therefore be lower than the estimate. The reference method for establishing it remains indirect calorimetry, which the manual names as the standard.
Sources
- InBody 970 Result Sheet Interpretation (ENG_A_211104) — InBody Co., Ltd.
- Bioelectrical impedance analysis in body composition measurement: NIH Technology Assessment Conference Statement — National Institutes of Health
- Bioelectrical impedance analysis – part II: utilization in clinical practice — Clinical Nutrition (ESPEN guidelines)
On this page
Related values
Commonly confused with
Related articles
Where to find it
The Visceral Fat Analysis, circumferences and basal metabolic rate.
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- MojeInBody content team
- Date
An InBody measurement is not a diagnostic tool. Results do not determine health status and do not replace a medical examination.
FAQ
Frequently asked questions
Answers to what people ask most often about this value.
Can I eat exactly as many calories as my BMR?
No. BMR covers only resting functions, not movement, ordinary daily activity and digestion. A daily intake set at the level of basal metabolic rate is well below actual expenditure for most people.
Why did I get a different BMR from an online calculator?
Ordinary calculators work from age, sex, height and weight. InBody uses an equation based on fat free mass, which it establishes by measurement. The results are therefore not interchangeable and a difference alone does not mean an error.
Will eating more often raise my BMR?
In this calculation the value moves only with a change in fat free mass. The manual gives gaining muscle mass as the route to a higher basal metabolic rate, not adjusting meal frequency.
Why does my BMR shift slightly at every measurement?
Because the fat free mass estimate it is calculated from fluctuates. A difference of one kilogram of FFM corresponds to roughly 22 kcal, so even ordinary variation in hydration shows in the number.
Explanations make the most sense alongside your own trend.
The public guide is open to everyone. The client portal adds your own value, history and the context of a specific measurement.