InBody Body Composition Test: What It Measures and What the Results Mean

Most people who come in for an InBody test have already had one somewhere. A gym, a wellness centre, a hospital package. They got a printout, looked at the numbers, and had no idea what to do with them. That is the part nobody seems to explain well.

If you are an expat living in Bangkok, this test is one of the most useful things you can do for a quick health check. The city makes it easy to sit at a desk all day, eat well, drink regularly, and still feel fine. The InBody result sheet is often the first time someone realises their body composition does not match how they feel. At Doctor Bangkok, we review these results with patients face to face, in English, and connect them to the bigger picture of their health.

How the InBody Test Works

The InBody uses a method called bioelectrical impedance analysis. A very small electrical current, completely painless, passes through your body via the hand grips and foot pads. Muscle conducts the current well because it holds a lot of water. Fat and bone resist it.

What I tell patients is: this is not a gym-grade scale. The device sends currents at several different frequencies, which lets it distinguish between fluids inside your cells and fluids outside them. That matters for accuracy. Older single-frequency devices fill in the gaps with population estimates. The InBody measures directly.

What Your Result Sheet Actually Shows

The printout can look overwhelming. Here is how I walk patients through it.

Skeletal Muscle Mass and Body Fat Mass

These two numbers sit at the top for a reason. Skeletal muscle mass is the muscle you can build and lose. Body fat mass is total fat in your body. The goal for most people is not just to lose fat. It is to maintain or grow muscle while fat comes down. You can lose weight on a scale and still be in a worse metabolic position if that weight was muscle.

Body Fat Percentage

This is more useful than weight alone. A healthy range is roughly 10 to 20 percent for men and 18 to 28 percent for women, though this shifts with age. I use this number alongside visceral fat level rather than in isolation.

Visceral Fat Level

This is the one most people underestimate. Visceral fat sits around your internal organs, deep in the abdomen. It is not the fat you can pinch. It raises your risk of insulin resistance, cardiovascular disease, and metabolic syndrome. The InBody scores visceral fat on a scale of 1 to 59. A level above 10 is where I start a clinical conversation.

Some patients look lean but have a high visceral fat score. That is the combination I worry about most. You can also have visible belly fat that is mostly subcutaneous, which is far less dangerous.

Basal Metabolic Rate

This is the number of calories your body burns at rest. It is driven largely by your muscle mass. More muscle means a higher basal metabolic rate. Crash diets that burn through muscle pull this number down, which is one reason weight regain happens so easily after rapid weight loss.

Segmental Muscle Analysis

The InBody breaks down muscle mass by body segment: right arm, left arm, trunk, right leg, left leg. This is genuinely useful. A lot of expats who sit at a desk have reasonable overall muscle mass but very low leg muscle. Leg muscle matters a great deal for long-term metabolic health and mobility.

Body Mass Index

BMI is on the sheet, but I rarely lead with it. It does not distinguish between muscle and fat. A muscular patient can have a BMI in the overweight range and excellent body composition. Use it as one data point, not the main verdict.

Advanced Metrics: Phase Angle and ECW/TBW Ratio

These two numbers appear on every InBody sheet. Almost no gym or wellness centre explains them. They are, in my view, two of the most clinically interesting outputs.

Phase Angle

Phase angle reflects how well your cells are holding their structure and fluid. A higher phase angle generally means healthier, more intact cells. A low phase angle can suggest inflammation, muscle wasting, or poor nutritional status. It is not a diagnostic test on its own, but in a patient whose other markers also look off, a low phase angle prompts a deeper look.

For adults in reasonable health, a phase angle above 5 degrees is generally reassuring. Below 4 degrees in a younger person is worth discussing with a doctor.

ECW/TBW Ratio

Your body water divides into two compartments: water inside your cells and water outside them. ECW/TBW is the ratio of outside-cell water to total body water. In a healthy body, this sits between 0.36 and 0.39. When it rises above 0.39, fluid may be shifting outside your cells. That can reflect inflammation or early kidney or liver changes.

This marker is not one you need to act on alone. But if your ratio is elevated, it is worth a conversation with a doctor rather than ignoring the number.

Who Should Not Take the InBody Test

The InBody is very safe for most people. There are a few situations where it is not appropriate.

If you have a pacemaker or an implanted cardiac defibrillator, do not use the InBody. The electrical current can interfere with the device. Pregnant women are advised to skip it. If you have significant visible fluid retention in your legs or abdomen, the results will likely distort several readings. If you have metal surgical implants in your limbs, speak to a clinician before proceeding.

At Doctor Bangkok, we ask about all of these factors before the test. If you are unsure, raise it during your consultation.

How to Prepare for the Best Results

Preparation matters more than most people realise, especially in Bangkok’s climate.

Test at the same time of day each visit. Morning before eating is ideal. Avoid food and drink for two to three hours before the test. Skip intense exercise for the twelve hours prior. Remove shoes, socks, and any metal jewellery. Bangkok heat causes more fluid loss through sweating than people account for, so arrive normally hydrated rather than dehydrated or having just downed a litre of water.

Alcohol the night before will affect your hydration balance and shift your results. If you had a big night, reschedule.

How Often Should You Retest

Testing every six to eight weeks is enough for most people tracking general health. That gives your body enough time for measurable changes in muscle or fat to show up. If you are actively managing your weight or adjusting medications that affect body composition, every four to six weeks gives you more useful data.

Testing weekly is almost never helpful for body composition. What changes week to week is body water, and those daily fluctuations can make your results look very different for no clinical reason.

What Your InBody Results Can Reveal About Metabolic Health

One pattern I see fairly often in Bangkok expats is something called sarcopenic obesity. Weight is in the normal range, BMI looks fine, but skeletal muscle mass is low and visceral fat is elevated. It is a combination that carries real metabolic risk but often goes undetected because the person does not look or feel overweight.

A quick gym scan without clinical review can miss this entirely. A doctor looking at the full result sheet alongside your age, lifestyle, and medical history can identify patterns that justify further testing or lifestyle changes before anything becomes a problem. Our diagnostics service at Doctor Bangkok includes exactly that kind of review.

Getting Your InBody Test at Doctor Bangkok

At Doctor Bangkok, the InBody body composition test is part of our diagnostics service. What makes this different from a gym scan is what happens after the printout. An English-speaking physician reviews every section of your result sheet with you. We connect the numbers to your actual health picture: your activity level, your diet, any symptoms you have raised, your travel health history, and any medications you are on.

The clinic is BTS accessible on Sukhumvit, which makes it convenient whether you live here or are visiting. Walk-ins are welcome. If you want to book ahead, you can do that through the Doctor Bangkok website.

If you are new to Bangkok and getting your bearings with healthcare here, a body composition assessment alongside a general health check is one of the most practical starting points I can suggest. You leave with real data and a doctor who has explained what it means.