What your scales can't tell you about visceral fat, muscle loss and your metabolic health

Your scales tell you one thing: how much gravity is pulling on your body. They do not tell you what that weight is made of, and that is precisely where the most important metabolic information lives.

Visceral fat, the fat stored deep around your organs, and skeletal muscle mass are invisible to the scales. They are also two clinically significant markers of metabolic health I measure in clinic. Together, they contribute to fatigue that rest doesn’t fix, inflammation that shows up as aches and joint pain, blood sugar instability, disrupted sleep, and the weight that settles around the middle and won’t shift regardless of what you eat. This article explains both: what they are, how they interact, and what measuring them actually makes possible.

What is visceral fat, and why does your muscle mass matter?

Body composition is the breakdown of your total weight into its component parts: muscle, fat, water, and bone. Of these, two are particularly significant for metabolic health.

The first is skeletal muscle mass — the metabolically active muscle that does most of the work in your body. Not aesthetic muscle; functional muscle. The kind that keeps your metabolism running, clears glucose from your bloodstream after meals, and produces anti-inflammatory signals every time it contracts.

The second is visceral fat — the fat stored deep inside the abdominal cavity, around your organs. This is distinct from the subcutaneous fat you can pinch beneath the skin. Visceral fat is biologically active. It secretes inflammatory proteins and hormones into the bloodstream, many of which drain directly into the liver. A higher level means more of these signals circulating continuously, not just in response to illness or injury.

Both are measurable. Most people have never had either measured.

What does an InBody scan show, and how does it work?

The InBody 270 is a body composition analyser of the kind used in clinical and sports science settings. The scan takes around 15 seconds. You stand on the device barefoot, hold two handles, and it passes a small, painless current through the body. Different tissues — muscle, fat, water — conduct that current differently. From those differences, it builds a detailed picture of what your weight is actually made of.

Your results show your skeletal muscle mass, body fat percentage, basal metabolic rate (the energy your body uses just to keep running at rest), and a visceral fat level score. It also stores previous scans, so over time you can see how the picture is moving, even when the scales show no change at all.

I always read the scan alongside the clinical picture: your history, your symptoms, and what you have already tried. Numbers without context are just numbers. The scan’s job is to make the invisible visible, and give us concrete data to utilise.

Why the ratio of visceral fat to muscle mass matters more than either number alone

The real insight is not just the visceral fat level or the muscle mass in isolation. It is the relationship between the two.

Think of skeletal muscle as your metabolic engine: the tissue that drives energy production, clears fuel from the blood, and keeps inflammation in check. Visceral fat is the drag on that engine — an active source of inflammatory signals working against the very processes muscle is trying to support.

The balance between them — how much engine you have relative to how much drag — is one of the most informative measures of metabolic health available without invasive testing. Research consistently shows that people with lower muscle mass relative to their visceral fat have higher insulin resistance, higher rates of metabolic syndrome, and a greater risk of chronic disease, regardless of their total body weight or BMI. [1,2,3,4]

In clinic, I call this the Metabolic Engine Score.

A body with good muscle mass and modest visceral fat has a favourable score: a strong engine with low drag. One with low muscle and high visceral fat has an unfavourable score: a weakened engine working against a significant headwind. The scales would show both of these as “normal weight.” The scan tells a very different story.

Visceral fat symptoms: what high visceral fat is doing inside your body

Visceral fat does not sit quietly. It produces a continuous low-level inflammatory signal — proteins your body uses as alarm calls — that travel through the bloodstream to the liver, the brain, the joints, the blood vessels, and the pancreas. [5] This is not the acute inflammation of a minor cut, which resolves as it heals. It is a background hum of inflammatory activity that rarely announces itself clearly, but accumulates over time.

There is a second mechanism that is less well known. Visceral fat has two to four times more cortisol receptors than the fat stored just beneath the skin. [6] Chronic stress drives cortisol up; cortisol drives visceral fat accumulation; visceral fat, in turn, stimulates further stress hormone output. It is a loop, and it tends to compound quietly, particularly in midlife. [6]

Why muscle mass is your body’s built-in defence against inflammation

Skeletal muscle, particularly when it is active, works in the opposite direction. Every time muscle contracts, it releases its own anti-inflammatory signals. These are a direct counterweight to the inflammatory signals visceral fat produces, and help the body respond to insulin and protect metabolic function. [7] Muscle also clears approximately 70–80% of the glucose you eat from the bloodstream after meals, a process that becomes less efficient when muscle mass is low. [8,9]

This is why body composition matters independently of diet. You can eat well and still have impaired glucose handling if the muscle to clear it is not there. You can exercise and still carry a chronic inflammatory background if the visceral fat driving it has not shifted. The picture requires both.

The signs of insulin resistance, and why body composition is the missing piece

When the Metabolic Engine Score is unfavourable — high visceral fat, low muscle — insulin resistance tends to follow. Many of the symptoms people bring to clinic trace back to exactly this.

Insulin is the hormone that moves glucose from the bloodstream into your cells after eating. In insulin resistance, cells stop responding to that signal as efficiently. The body compensates by producing more insulin. For a period, blood glucose stays relatively normal, but the system is under increasing strain. What tends to show up in the meantime is not yet a diabetes diagnosis. It is the cluster of symptoms that sit upstream of one: persistent fatigue, blood sugar crashes, weight accumulating around the middle despite dietary effort, mood that drops in the afternoon, sleep that does not fully restore.

Visceral fat drives insulin resistance through three overlapping pathways: it releases fatty acids directly into the liver, impairing glucose regulation; it releases inflammatory signals that interfere with insulin’s action in muscle cells; and as visceral fat expands, the body’s own anti-inflammatory and insulin-sensitising hormones decline. [10,11] Low muscle mass compounds the problem by reducing the tissue available to clear glucose in the first place. [8,9]

The scan does not diagnose insulin resistance. What it does is show the conditions in which it develops: low muscle, high visceral fat, a metabolism running below where it should be. The clinical picture does the rest.

Could visceral fat be behind your fatigue, aches, poor sleep and mood changes?

These symptoms are not separate problems. They are different expressions of the same underlying metabolic picture.

Fatigue and poor sleep often travel together. Low muscle mass reduces the body’s baseline energy output, and when the mitochondria (the tiny energy-producing structures inside muscle cells) are working less efficiently, that decline goes further. [12] The tiredness that rest doesn’t fix is often a sign of exactly this. Sleep suffers through a related mechanism. The cortisol-visceral fat relationship means that elevated cortisol, particularly in the evening, is associated with lighter, more disrupted sleep and suppression of REM sleep. [6,13] Many people with persistently poor sleep have elevated evening cortisol, and visceral fat is one of the less-discussed reasons why.

The same inflammatory signals that disrupt energy and sleep also reach the joints. Visceral fat-driven inflammation is not localised; it travels through the bloodstream, and for many people, joints and connective tissue are where they notice it most. A 2025 study of nearly 6,000 adults found a significant association between visceral fat score and chronic pain, independent of body weight. [14]

Blood sugar and blood pressure connect closely to the same picture. Low muscle mass reduces glucose clearance capacity; high visceral fat impairs insulin signalling at multiple levels. Together, that is the most direct route to prediabetes. [10,11] Raised blood pressure connects through two routes. Visceral fat-driven inflammation impairs the lining of blood vessels, reducing their ability to relax and dilate. [5] And as insulin resistance develops, the body produces more insulin to compensate; higher circulating insulin levels are associated with raised blood pressure, in part through their effects on the kidneys and the sympathetic nervous system. [20]

Stress and mood changes round out the picture. The cortisol-visceral fat loop runs in both directions: chronic stress accumulates visceral fat, which drives further cortisol output, which drives further accumulation. [6] And the inflammatory signals released by visceral fat cross into the brain. Research links visceral fat specifically to anxiety and depression through neuroinflammatory pathways. [15,16]

Menopause belly fat and muscle loss: what’s really happening to your body

For women in perimenopause and beyond, this picture matters in a particular way, because the menopause transition is when body composition changes most dramatically, and most invisibly.

Research shows that visceral fat approximately doubles during the transition. [17,19] Lean muscle mass declines simultaneously. Any change on the scales often seems out of proportion to diet or lifestyle, because the composition shift is happening underneath it. The increases in abdominal fat directly parallel the fall in oestradiol: oestrogen is not only a reproductive hormone; it actively maintains muscle tissue and limits visceral fat accumulation. As oestrogen declines, both of those protections are withdrawn at once. [17,18]

The result is that many of the symptoms attributed to “just menopause” — the fatigue, the aching joints, the disrupted sleep, the mood that is harder to manage — have a body composition component that is rarely assessed. Hot flushes too: disrupted glucose handling can lower the thermoregulatory threshold and trigger the sympathetic nervous system responses that manifest as night sweats. [21,22]

None of this means HRT is not relevant, or that lifestyle is the only answer. It means there is more going on beneath the surface than most assessments capture, and that measuring it opens up more options.

Body composition measurement during this transition is not optional extra information. It is the baseline that makes a structured programme meaningful. There is growing evidence of the metabolic connection to menopause symptoms directly: higher fasting insulin levels in early perimenopause have been associated with earlier onset and longer duration of hot flushes and night sweats, independent of body weight. [21,22] It tells you where muscle and visceral fat sit before any intervention begins, tracks what is actually shifting as the programme progresses, and captures change that weight alone would miss entirely. For women going through perimenopause and beyond, that data is often the first clear picture they have had of what is driving how they feel.

Beyond BMI: what a body composition scan, report and personal guide actually gives you

A number without context is just a number. What the Root Cause Clinic appointment gives you is interpretation.

During the appointment, I work through your key markers with you and connect them to what you have been experiencing: low energy, poor blood sugar control, inflammation, joint pain, brain fog, anxiety or low mood. Your scan results, together with your clinical history, give us a clear starting point.

You will receive a detailed body composition report, a guide explaining how to optimise your results, and a personalised metabolic action plan covering the specific nutrition, movement, and lifestyle changes most likely to shift the picture, based on your scan and your daily life.

And because the InBody stores previous scans, every follow-up appointment shows how the picture has moved. Muscle increasing, visceral fat reducing: progress the scales would never show, but the scan does.

You can explore what the report looks like before booking at drrebeccahiscutt.com/sample-report.html.

This is the starting point, not the verdict

Body composition can improve at any age and any stage. The biology is genuinely responsive: visceral fat is reducible, muscle is buildable, and the metabolic picture shifts more quickly than most people expect once the right foundations are in place.

The difficulty is that most people have been trying to address these symptoms without ever knowing what was driving them. They have been watching a number on the scales that was never going to show them the answer.

The scan gives you the answer the scales cannot. And that is where the work, and the progress, actually begins.

A Root Cause Clinic appointment includes a full InBody 270 body composition scan, a detailed body composition report, a guide to optimising your results, and a personalised metabolic action plan. Book your appointment

Questions I’m often asked

Is this only relevant for women?

No. Visceral fat accumulation and muscle loss affect men too, and the mechanisms are identical. In men, the hormonal driver is a gradual decline in testosterone from the 40s onwards, which plays a similar role in maintaining muscle to oestrogen in women. The Metabolic Engine Score applies equally, and the symptoms — fatigue, aches, blood sugar changes, disrupted sleep, mood changes — are the same.

My BMI is normal. Could this still apply to me?

Yes, and this is one of the most important points. BMI does not measure body composition. A person can have a completely normal BMI with a Metabolic Engine Score pointing in the wrong direction, because visceral fat has crept up quietly while muscle has declined. Researchers call this “normal weight sarcopenic obesity.” The scales look fine. The underlying metabolic picture does not.

Could this explain symptoms I’ve been putting down to stress or age?

Quite possibly. Chronic fatigue, joint aches, disrupted sleep, and mood changes that have accumulated gradually are exactly the kind of symptoms that tend to have a metabolic component. The fact that they have built up slowly, without a clear cause, is actually a feature of how body composition shifts: quietly, over time, below the threshold of any single test or consultation.

How often should I be scanned?

I recommend a follow-up scan at 8 weeks, then monthly. One scan tells you where you are. Repeat scans show you where you are going.

This article is for informational purposes only and does not constitute medical advice. If you have concerns about your health, please consult your GP or a registered healthcare professional.