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If you truly want to understand what is happening inside your body — bone strength, skeletal muscle mass, and fat distribution — medical imaging is the only approach with sufficient accuracy to support best medical practice.
“Body composition” is not a cosmetic concept. It directly relates to outcomes that matter clinically and personally: hip fracture, vertebral compression and spinal collapse in later life, frailty, insulin resistance, cardiometabolic disease, and increasingly recognised risks such as dementia. Decisions based on imprecise measurements risk false reassurance, delayed intervention, or inappropriate therapy.
The challenge is that many commonly used metrics — weight, BMI, and consumer “smart” devices — create an illusion of precision. They provide numbers, but not necessarily truth. When it comes to guiding therapy, prevention, or long-term health planning, approximation is not enough.
What clinicians actually mean by body composition
In clinical medicine, meaningful body composition assessment rests on three pillars:
- Bone mineral density (BMD) – a predictor of osteoporosis and fracture risk
- Skeletal muscle mass – central to metabolic health, resilience, and healthy ageing
- Adipose tissue distribution – particularly visceral adipose tissue (VAT)
Each pillar predicts different outcomes. Bone density predicts fracture and loss of independence. Muscle mass predicts strength, recovery from illness, insulin sensitivity, and longevity. VAT predicts cardiometabolic risk far more powerfully than body weight alone.
Each pillar is best assessed using medical imaging.
Why bioimpedance does not meet medical standards
Most home “body composition” scales use bioimpedance analysis. A small electrical current is passed through the body, and lean mass and fat mass are inferred using proprietary algorithms.
The limitations are substantial:
- Hydration status, salt intake, alcohol, recent exercise, and time of day materially alter results
- The technology cannot identify where fat is stored
- Algorithms rely on assumptions that often fail in older adults, athletic individuals, and those with sarcopenia
Even professional-grade systems do not carry sufficient accuracy to govern medical decision-making or therapy. At best, they provide directional trends.
Where body composition scales do have an important role
Despite these limitations, body composition scales are a valuable part of our metabolic toolkit in patients with metabolically unhealthy visceral adipose tissue.
They are not used diagnostically. Instead, they are deployed as home-based tracking tools, providing frequent feedback between formal medical measurements.
When used consistently, they can:
- Demonstrate directional change in fat and lean mass
- Reassure patients during weight plateaus
- Reinforce adherence to nutrition and resistance training
Most importantly, they act as a powerful driver of behavioural change.
Tracking drives behaviour change — not measurement perfection
Sustained reduction in visceral adipose tissue requires behavioural change maintained over months. Behaviour change without feedback rarely succeeds.
This is why we combine home body composition scales with:
- Continuous glucose monitoring (CGM) to identify glucose and insulin spikes
- Food analysis apps to optimise protein intake and energy balance
- Serial waist measurements to track central fat reduction
- Periodic medical imaging (DEXA and CT) as accurate anchor points
Together, these tools form a closed-loop system:
education → action → feedback → adjustment.
The aim is to gradually lower the defended set point for weight and VAT — the physiological goal that underpins durable metabolic improvement.
DEXA: the gold standard for bone density and lean mass
Dual-energy X-ray absorptiometry (DEXA) is the internationally recognised gold standard for assessing bone mineral density and diagnosing osteoporosis¹. Guidance from the International Society for Clinical Densitometry defines its clinical use and interpretation¹.
DEXA:
- Identifies low bone density before fracture occurs
- Allows risk stratification and early intervention
- Provides a reliable baseline for longitudinal monitoring
DEXA also provides robust estimates of lean mass, commonly used in sarcopenia assessment.
Radiation exposure and access
The radiation dose from DEXA is extremely low, typically well below that of a chest X-ray². This favourable safety profile allows direct access DEXA scanning in appropriate settings.
DEXA is excellent for bone and muscle assessment, but it is not the optimal tool for measuring visceral adipose tissue.
We offer direct access to DEXA, get in touch and one of our patient care coordinators will let you know pricing and availability.
Visceral adipose tissue: the fat that drives disease
Visceral adipose tissue is biologically active fat stored around abdominal organs. Unlike subcutaneous fat, VAT drives:
- Insulin resistance and type 2 diabetes
- Atherogenic dyslipidaemia
- Chronic inflammation
- Hypertension and metabolic syndrome
- Cardiovascular disease
- Dementia and certain cancers
VAT is therefore one of the most important modifiable risk factors in modern medicine.
Importantly, VAT cannot be reliably inferred from weight, BMI, or appearance.
MRI and CT: accurate tools for VAT measurement
The most accurate methods for VAT measurement are MRI and CT.
MRI avoids ionising radiation but is slower and less accessible. CT is fast, widely available, and highly reproducible. Modern scanners allow substantial dose reduction compared with traditional abdominal CT³.
Large studies demonstrate that VAT measured from a single cross-sectional slice correlates strongly with total VAT volume⁴⁵.
Our low-dose single-slice CT VAT scan
Based on this evidence, at VCL/SCVC we use a very low-dose single-slice CT VAT scan.
Peer-reviewed radiology literature confirms that VAT can be accurately measured using a single CT slice, with an effective radiation dose of approximately 1 mSv — around 10 % of the dose of a standard abdominal CT⁷.
Using modern dose modulation, this provides:
- High reproducibility
- Accurate reflection of overall VAT burden
- Suitability for longitudinal tracking
This dose is approximately one quarter of that of a mammogram and far below historical abdominal CT exposures³,⁷.
Why VAT measurement matters in the GLP-1 era
GLP-1 receptor agonists have transformed cardiometabolic care. Their benefit extends beyond weight loss.
In the SELECT trial, semaglutide significantly reduced major adverse cardiovascular events in patients with established cardiovascular disease and overweight or obesity without diabetes⁶.
A highly plausible mechanism is preferential reduction in visceral adipose tissue, with downstream improvements in insulin resistance, lipid metabolism, and inflammation.
If cardiovascular risk reduction is the goal, VAT is the metric that matters.
Muscle mass: the overlooked determinant of outcome
Weight loss without muscle preservation increases frailty risk and undermines metabolic health.
Skeletal muscle underpins glucose disposal, metabolic flexibility, physical independence, and long-term weight maintenance. Our CT VAT report therefore also estimates skeletal muscle mass, allowing personalised protein targets:
- ≥ 0.8 g/kg/day minimum
- ~ 1.2 g/kg/day for most adults
- Higher targets during weight loss or GLP-1 therapy
Example VAT Report Blog
Access, justification, and safeguards
Radiation reassurance: what does a low-dose VAT CT actually mean?
Understandably, many patients are concerned when they hear the word CT scan. Much of that concern relates to experiences with full abdominal CT, which historically carried higher radiation doses.
The VAT scan we use is very different.
- It is a single-slice CT scan, not a full abdominal study
- It is performed using modern dose-modulated CT technology
- The typical effective radiation dose is around 1 mSv
To put this into context:
- A standard abdominal CT is typically 8–10 mSv or more
- A mammogram is approximately 4 mSv
- Natural background radiation in the UK averages ~2.7 mSv per year
This means the radiation exposure from a VAT scan is:
- About 10% of a conventional abdominal CT
- Around a quarter of a mammogram
- Less than half of annual background radiation
Crucially, the scan provides clinically meaningful information about visceral fat — one of the most important modifiable drivers of cardiometabolic risk — using a dose that is considered low and proportionate when appropriately justified.
We do not offer this scan indiscriminately. Every scan is:
- Clinically justified
- Reviewed via a pre-consultation pathway
- Avoided in situations where it may cause harm or anxiety
In short, this is a targeted, low-dose investigation, designed to give high-value information while keeping radiation exposure as low as reasonably achievable.
All CT imaging must be clinically justified.
At SCVC and VCL, we operate a free pre-consultation pathway using a structured questionnaire. When criteria are met, scans can be arranged without formal clinic consultation.
The bottom line
If accuracy matters, medical imaging is essential.
- DEXA is the gold standard for bone density and lean mass¹²
- Low-dose CT or MRI are required for accurate VAT measurement⁴⁵⁷
- Home tools — body composition scales, CGM, food analysis apps, and waist measurements — are powerful behaviour-change drivers
Precision provides the anchor. Tracking provides the momentum. Together, they enable the sustained behavioural change required to lower the defended set point for weight and visceral adipose tissue.
If you are interested in finding out more, use our enquiry form and a patient care coordinator will get in touch.
References
- International Society for Clinical Densitometry (ISCD).2023 ISCD Official Positions – Adult. Middletown (CT): ISCD; 2023.Available from:https://iscd.org/wp-content/uploads/2024/03/2023-ISCD-Adult-Positions.pdf
- International Atomic Energy Agency (IAEA).Radiation protection of patients during DEXA (bone mineral densitometry). Vienna: IAEA; n.d.Available from:https://www.iaea.org/resources/rpop/health-professionals/other-specialities-and-imaging-modalities/dxa-bone-mineral-densitometry/patients
- RadiologyInfo.org (American College of Radiology; Radiological Society of North America).Radiation dose from X-ray and CT examinations.Available from:https://www.radiologyinfo.org/en/info/safety-xray
- Shen W, Punyanitya M, Wang Z, Gallagher D, St-Onge MP, Albu J, et al.Visceral adipose tissue: relations between single-slice areas and total volume. Am J Clin Nutr. 2004;80(2):271–278.Available from:https://pmc.ncbi.nlm.nih.gov/articles/PMC2040041/
- Demerath EW, Ritter KJ, Couch WA, Rogers NL, Moreno GM, Choh AC, et al.Approximation of total visceral adipose tissue with a single magnetic resonance image. Am J Cardiol. 2007;100(9):1444–1449.Available from:https://www.sciencedirect.com/science/article/pii/S0002916523279204
- Lincoff AM, Brown-Frandsen K, Colhoun HM, Deanfield J, Emerson SS, Esbjerg S, et al.Semaglutide and cardiovascular outcomes in patients with overweight or obesity without diabetes (SELECT). N Engl J Med. 2023;389:2221–2232.Available from:https://www.nejm.org/doi/full/10.1056/NEJMoa2307563
- Shuster A, Patlas M, Pinthus JH, Mourtzakis M.The clinical importance of visceral adiposity: a critical review of methods for visceral adipose tissue analysis. Br J Radiol. 2012;85(1009):1–10. doi:10.1259/bjr/38447238.Available from:https://pmc.ncbi.nlm.nih.gov/articles/PMC3473928/
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