The Complete DEXA Scan Guide
Everything you need to understand your body composition results — written in plain English, backed by clinical evidence.
In this guide
Body Fat Percentage
The most misunderstood number on your report
Body fat percentage is the proportion of your total weight that is fat tissue. Unlike the number on a bathroom scale, it tells you something meaningful — how much of you is metabolically active muscle versus stored energy.
DEXA is the gold standard for measuring body fat because it distinguishes between fat, lean tissue, and bone across every region of your body — something no scale, BMI calculation, or hand-held device can accurately do.
Body Fat % Reference Ranges
| Category | Men | Women |
|---|---|---|
| Essential Fat | 2–5% | 10–13% |
| Athletic | 6–13% | 14–20% |
| Fit / Healthy | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Overweight | 25–29% | 32–37% |
| Obese | 30%+ | 38%+ |
Ranges are for adults aged 20–59. Optimal body fat increases slightly with age.
Key insight
A common misconception: being in the 'normal' BMI range doesn't mean your body fat is healthy. Many people with normal BMI have high body fat and low lean mass — a condition called 'skinny fat' or normal-weight obesity, which carries significant metabolic risk.
The goal is not to minimise body fat at all costs. Essential fat is critical for hormone production, organ protection, and neurological function. For most people, the sweet spot is the 'fit/healthy' range — low enough to support good insulin sensitivity, high enough to maintain hormonal health.
Lean Mass
Your most important longevity metric
Lean mass includes everything that isn't fat — primarily muscle, but also water, organs, and connective tissue. Your DEXA report will show lean mass in kilograms or pounds, often broken down by body region (arms, legs, trunk).
Muscle mass is arguably the most powerful predictor of long-term health outcomes. Research consistently links higher lean mass to lower all-cause mortality, better insulin sensitivity, reduced fall risk, faster recovery from illness, and improved cognitive function as we age.
Average Lean Mass by Sex
| Sex | Average Lean Mass | Above Average |
|---|---|---|
| Men | ~130–145 lbs (59–66 kg) | > 145 lbs (66 kg) |
| Women | ~95–110 lbs (43–50 kg) | > 110 lbs (50 kg) |
Values vary with height. Taller individuals naturally carry more lean mass.
Key insight
Sarcopenia — age-related muscle loss — begins as early as your 30s at a rate of 3–8% per decade. After 60, this accelerates. The best insurance against sarcopenia is building a strong lean mass baseline now and maintaining it with progressive resistance training.
The most effective interventions for increasing lean mass are progressive resistance training (3+ sessions per week) and adequate protein intake. Research supports a target of 0.7–1.0g of protein per pound of body weight per day for adults focused on muscle preservation or growth.
DEXA is uniquely useful for tracking lean mass because it reveals regional distribution. If your arms are gaining muscle but your legs aren't, that shows up. Asymmetries between left and right limbs — which can indicate injury compensation — are also visible.
Visceral Fat
The fat that matters most for your health
Visceral fat is the fat stored deep inside your abdominal cavity, surrounding your liver, pancreas, kidneys, and intestines. Unlike subcutaneous fat (the fat you can pinch under your skin), visceral fat is metabolically active — it secretes inflammatory cytokines and hormones that disrupt insulin signalling, raise blood pressure, and promote cardiovascular disease.
You cannot estimate visceral fat by looking in the mirror or stepping on a scale. Two people with identical waist measurements can have dramatically different amounts of visceral fat. DEXA measures it directly.
Visceral Fat Risk Levels
| Level | Mass | Health Implication |
|---|---|---|
| Healthy | < 2 lbs (< 0.9 kg) | Low metabolic risk |
| Borderline | 2–3 lbs (0.9–1.4 kg) | Elevated risk — monitor and act |
| High | > 3 lbs (> 1.4 kg) | Significant cardiovascular and metabolic risk |
Key insight
Visceral fat responds faster to lifestyle intervention than subcutaneous fat. Studies show that even modest weight loss of 5–10% of body weight can reduce visceral fat by 10–30%. It's the most 'moveable' fat in your body — and reducing it has immediate metabolic benefits.
The most effective interventions for reducing visceral fat are: caloric deficit (even modest reduction of 300–500 kcal/day), cardiovascular exercise (150+ minutes per week at moderate intensity), reducing refined carbohydrates and added sugars, improving sleep quality (poor sleep directly increases visceral fat deposition), and managing chronic stress (cortisol drives visceral fat storage).
High visceral fat is independently associated with Type 2 diabetes, cardiovascular disease, certain cancers, non-alcoholic fatty liver disease, and all-cause mortality — even in people who appear otherwise healthy by weight or BMI.
Bone Mineral Density
Your structural foundation — and a long-term investment
Bone Mineral Density (BMD) measures how much mineral content — primarily calcium and phosphorus — is packed into your bone tissue. The higher your BMD, the stronger your bones and the lower your fracture risk.
Your DEXA report expresses BMD as a T-score: the number of standard deviations your bone density is above or below the average peak bone density of a healthy young adult of your sex. This standardisation makes it easy to compare across machines and labs.
BMD T-Score Classification (WHO Criteria)
| T-Score | Classification | Fracture Risk |
|---|---|---|
| -1.0 and above | Normal | Low |
| -1.0 to -2.5 | Osteopenia | Moderately elevated — act now |
| Below -2.5 | Osteoporosis | High — medical evaluation recommended |
Key insight
Bone density peaks in your late 20s and declines slowly from there. Women experience accelerated bone loss in the years around menopause due to falling oestrogen levels — losing up to 20% of bone density in the first 5–7 years post-menopause. Men lose bone more gradually but are not immune to osteoporosis.
Osteopenia is not a disease — it's a warning. It means your bone density is below optimal but not yet in the osteoporosis range. This is the ideal time to intervene. Key actions: weight-bearing resistance training (proven to increase BMD), adequate calcium (1000–1200mg/day from food or supplements), Vitamin D3 (2000–4000 IU/day — most adults are deficient), and Vitamin K2 (helps direct calcium into bones).
Note that DEXA reports sometimes show separate T-scores for the spine, hip, and total body. These can differ significantly. The total body T-score gives the broadest picture, but your doctor may focus on the spine or hip scores for fracture risk assessment, as these are the most clinically relevant sites.
GLP-1 Medications & Body Composition
What Ozempic, Wegovy, and Tirzepatide do to your body — and why DEXA matters
GLP-1 receptor agonists (semaglutide, tirzepatide, liraglutide) have transformed weight loss medicine. Studies show average weight loss of 15–22% of body weight over 12–18 months — results previously only seen with bariatric surgery.
But here's what the scale doesn't tell you: not all weight loss is equal. When people lose weight — through any method — they lose a combination of fat mass and lean mass (muscle). The ratio matters enormously for long-term health.
Key insight
Studies of GLP-1 medications show that roughly 25–40% of weight lost is lean mass, not fat. This means someone losing 40 lbs on Ozempic might lose 10–16 lbs of muscle alongside 24–30 lbs of fat. Without DEXA tracking, this muscle loss is completely invisible.
Why does this matter? Muscle loss reduces metabolic rate, increases frailty risk, impairs glucose disposal, and makes weight regain more likely after stopping medication. Many clinicians now recommend resistance training and high protein intake alongside GLP-1 therapy to preserve lean mass — but without DEXA, there's no way to know if it's working.
DEXA every 3–6 months while on GLP-1 therapy is the only way to verify whether your weight loss is predominantly fat (good) or includes significant muscle loss (bad). If muscle loss is occurring, you can adjust protein intake, training intensity, or discuss the issue with your prescribing physician.
Visceral fat tracking is equally important on GLP-1s. These medications are particularly effective at reducing visceral fat — often disproportionately so compared to subcutaneous fat. DEXA lets you see this happening in real time, which can be a powerful motivator and a useful clinical data point.
What To Do With Your Results
Turning numbers into action
A DEXA scan is a starting point, not a verdict. The most important thing you can do with your results is use them to set specific, measurable targets and track your progress over time.
If your body fat % is high:
- Create a modest caloric deficit (300–500 kcal/day) — not a crash diet
- Prioritise resistance training to preserve muscle during fat loss
- Reduce refined carbohydrates and added sugars
- Aim for 7–9 hours of sleep — poor sleep sabotages fat loss
- Retest with DEXA in 3–6 months to measure progress
If your lean mass is below average:
- Start progressive resistance training 3x per week minimum
- Increase protein to 0.7–1.0g per lb of body weight
- Ensure adequate caloric intake — you can't build muscle in a deep deficit
- Prioritise compound movements: squats, deadlifts, rows, presses
- Be patient — meaningful lean mass gains take 3–6 months to show on DEXA
If your visceral fat is elevated:
- This is your highest priority — visceral fat carries the most health risk
- 150+ minutes of moderate cardio per week (walking counts)
- Reduce alcohol — it drives visceral fat accumulation directly
- Address sleep and stress — both are major visceral fat drivers
- Consider a low-carbohydrate or Mediterranean dietary approach
If your bone density is low (osteopenia/osteoporosis):
- Get a Vitamin D blood test — most people with low BMD are deficient
- Supplement: Calcium 1000–1200mg/day + Vitamin D3 2000–4000 IU/day + Vitamin K2 100–200mcg/day
- Weight-bearing exercise is essential — it's the only proven way to increase BMD
- Discuss with your doctor — osteoporosis may warrant prescription treatment
- Retest in 12 months — bone density changes slowly
Key insight
The single most powerful thing you can do for all four DEXA metrics simultaneously: start or intensify a progressive resistance training program. Resistance training reduces body fat, builds lean mass, reduces visceral fat, and increases bone density. No other intervention has this breadth of benefit.
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