You stood on a machine for sixty seconds and it handed you a page of numbers. Most gyms do not explain it, and the sheet itself only labels things. Here is what each number is, what moves it, and which ones are worth your attention.
The same number your bathroom scale gives you. It is the least useful line on the sheet, because it cannot tell you what changed. Two pounds of water, two pounds of fat and two pounds of muscle all read the same here.
Weigh yourself under the same conditions each time. Food, drink and salt move this by several pounds inside a day.
The muscle you can actually train, not counting your organs or the water around them. This is the number to want going up. It moves slowly: a pound a month is a good rate, and anything faster is usually water or a different hydration state rather than new muscle.
Do not confuse this with lean body mass, which is a bigger number that includes organs, bone and water. Gyms mix them up constantly.
Body fat mass is the weight of your fat in pounds or kilos. Percent body fat is that as a share of your total weight. Percent is the more useful of the two, because it moves when either fat or muscle changes.
The range used across exercise science is 20 to 32% for women and 10 to 22% for men.
Your sheet may disagree with that. InBody prints a narrower band, 18 to 28% for women, so the same reading can look fine against one and high against the other. Neither is wrong. They are different reference populations.
Weight divided by height squared. It knows nothing about what your weight is made of, so a muscular person reads as overweight and someone with very little muscle can read as normal while carrying a lot of fat.
18.5 to 25 is the band used internationally as healthy.
If you have a body composition sheet in your hand, you can ignore this line. Percent body fat answers the same question better.
All the water in your body. It sounds like a hydration reading and it is not really one: muscle is roughly three quarters water and fat is much less, so this number mostly tracks how much muscle you have.
Published population figures sit around 58% of body weight for men and 48% for women. That is a rough average, not a formal guideline.
A single reading moves with what you drank and ate. Watch the trend, not the day.
Your body water splits into water inside your cells and water outside them. This ratio is the outside share. It is the line most people skip and one of the more interesting ones, because it changes when something other than fat or muscle changes: swelling, inflammation, illness, a very hard training block, or poor sleep.
A rise with no change in weight or muscle is worth noticing, not worth panicking about. It is a prompt to look at sleep, salt and recovery, or to mention it to a doctor if it stays up.
Lean mass with the water taken out, so mostly protein and mineral. It moves slowly and steadily, which makes it a good sanity check: if your muscle number jumped but dry lean mass did not, you gained water, not muscle.
Muscle in each arm, each leg and your trunk, shown as a percentage of what is expected for your size. 100% means as expected. This is where an imbalance shows up, and it is the part of the sheet that most often tells you something you did not already know.
A gap of more than 10% between left and right is the line commonly treated as worth acting on. That threshold comes from strength testing, and applying it to body composition readings is an extension of it, not a settled standard.
Compare left against right, and also upper against lower. An arm-heavy or leg-heavy build does not show up in a left-right comparison at all.
The same breakdown for fat rather than muscle. Worth knowing: the InBody 270 does not print this on the paper sheet, but it does send it to the InBody phone app, under Segmental Analysis then Fat. So if your sheet has no fat breakdown, the reading still exists and the app has it.
An estimate of the calories you would burn doing nothing at all for a day. It is calculated from your lean mass rather than measured, so treat it as a starting point for setting a calorie target, not a fact about your body.
Your actual daily burn is higher, because you move. How much higher is guesswork on any device.
InBody's own 0 to 100 rating. How it is calculated is not published, so nobody outside InBody can tell you exactly what moved it or by how much.
A score you cannot decompose is hard to act on. It is fine as a rough direction and not worth chasing.
Four things, in this order. Skeletal muscle mass going up or holding. Percent body fat going down or holding. Left to right balance inside about 10%. And ECW/TBW staying flat. Everything else on the sheet is either derived from those or too noisy to read one reading at a time.
One reading is a data point, not a trend. Three readings over three months tell you something a single sheet never can.
InBody devices use bioelectrical impedance: a small current through your body, measuring how it resists. Muscle conducts well because it holds water. Fat does not. Everything on the sheet is worked out from that resistance and your height, age and sex.
Bodivio reads an InBody sheet from a photo and charts every reading, so you can see the year rather than the day. Every figure it shows says where it came from, the same way this page does.
Have a lookThis explains what the numbers on a body composition sheet mean. It is not medical advice, a diagnosis, or a substitute for talking to a doctor or a dietitian.