A DEXA scan measures your body composition: how much of your weight is fat, how much is lean tissue such as muscle, and how much is bone, and where each sits in your body. It answers a question the scales and your BMI cannot: whether the weight you have lost came off as fat or as muscle.
Dr Kumar asks every patient preparing for body contouring surgery to have a DEXA body composition scan. This page explains what the scan is, why it tells us more than BMI, how Dr Kumar uses it, and what it involves and costs.
What a DEXA scan is
DEXA stands for dual-energy X-ray absorptiometry (you may also see it written as DXA). The scanner passes two very low-dose X-ray beams of different energies across your body. Fat, lean tissue and bone absorb the two energies differently, so the machine can separate your weight into those three parts, region by region.
It is the same technology used to measure bone density. A body composition scan uses a whole-body pass rather than the hip and spine views of a bone density test.
A typical report shows:
- Total fat mass and body fat percentage
- Lean mass, which is mostly muscle, plus organs and water
- Appendicular lean mass, the muscle in your arms and legs, which is the measure most closely linked to strength and recovery
- Visceral fat, an estimate of the fat inside your abdomen around the organs
- Regional breakdown for the arms, legs and trunk, including where fat is concentrated
- Bone mineral content, with bone density where the provider includes it
Why BMI is not enough
Body mass index (BMI) is your weight in kilograms divided by your height in metres squared. It is quick and useful across large populations, and Medicare’s criteria for skin removal surgery are written around it. For an individual preparing for surgery, though, it leaves out most of what matters.
- It cannot tell fat from muscle. Two people with the same height and weight have the same BMI, even if one carries far more muscle than the other.
- It cannot show where fat is. Fat inside the abdomen behaves differently from fat under the skin, both for your health and for what surgery can change.
- It counts loose skin as body weight. After major weight loss, excess skin and the tissue within it can weigh several kilograms. BMI treats that the same as fat or muscle.
- It can hide muscle loss. It is possible to carry low muscle and relatively high fat at a BMI that looks unremarkable. This is called sarcopenic obesity, and it is common after rapid weight loss.
- A steady weight is not the same as a steady body. Your weight can hold still while you continue to lose muscle and regain fat. BMI will not show it; a repeat DEXA scan will.
Home scales that estimate body fat use bioelectrical impedance, which varies with hydration, food and time of day. They can show a trend, but they are not accurate enough to plan surgery around.
| What we want to know | BMI | DEXA |
|---|---|---|
| How much of your weight is fat | No | Yes |
| How much muscle you have, and where | No | Yes |
| Fat inside the abdomen versus under the skin | No | Estimate |
| Whether recent weight loss was fat or muscle | No | Yes, with a repeat scan |
| Bone health | No | Where bone density is included |
Why Dr Kumar asks for a DEXA scan before surgery
1. Muscle is your reserve for healing
Healing large wounds draws on protein, and your muscle is the body’s main protein store. Weight loss of any kind costs some muscle as well as fat, and fast weight loss can cost a lot. In published trials of weight-loss medicines that measured body composition by DEXA, lean tissue made up roughly a quarter to two-fifths of the weight lost. Loss after bariatric surgery can be similar.
Low muscle mass is linked to more complications after major surgery. In a 2020 review of gastrointestinal surgery, patients with properly diagnosed low muscle mass and strength had around three times the odds of postoperative complications. Body contouring has been studied less, but the principle is the same. A DEXA scan shows whether you are starting with enough reserve.
2. It gives your preparation a target
Every patient is introduced to Dr Kumar’s Accredited Practising Dietitian before surgery. Appointments are available in person or by telehealth. Your DEXA result lets the dietitian set protein and training goals for your body, rather than for an average person of your weight. Where lean mass is low, protein intake and resistance exercise become the priority before an operation is booked. For practical guidance on protein and resistance training while you are still losing weight, see protein and muscle during weight loss on My Weight Loss Journey, Dr Kumar’s guide to preparing for body contouring.
3. It shows what surgery can and cannot change
Body contouring removes excess skin and the fat beneath it, outside the muscle wall. It cannot remove fat inside the abdomen. If much of the fullness in your abdomen is visceral fat, an abdominoplasty (tummy tuck) or body lift will tighten the skin but the abdomen will not be as flat as it would be with less internal fat. Knowing this before surgery helps Dr Kumar plan the operation and helps you set realistic expectations.
4. It gives an objective baseline for weight stability
Dr Kumar plans surgery once your weight has been stable, because operating while weight is still changing compromises the result. A DEXA scan records your composition at a point in time. If there is any question about whether your body is still changing, a repeat scan answers it.
5. Bone health after bariatric surgery
Bone density can fall after some bariatric operations, particularly gastric bypass. Where your scan includes bone density, it adds useful information about your bone health. Anything unexpected is passed to your GP to follow up.
What it does not do
A DEXA scan does not decide whether you can have surgery, and no DEXA result qualifies you for a Medicare item. The Medicare items for skin removal after weight loss depend on weight loss of at least five BMI points, weight that has been stable for at least six months and the functional problems caused by the excess skin. How the Medicare criteria work.
What the scan involves
| Step | What to expect |
|---|---|
| Time | About 10 to 15 minutes in total. The scan itself takes a few minutes, lying still on your back on an open table. |
| What you feel | Nothing. There is no tunnel and no injection. The scanner arm passes over you. |
| Clothing | Light clothing with no metal: no zips, buttons, underwire or jewellery. Some providers supply a gown. |
| Radiation | Very low. A whole-body DEXA scan typically gives between 0.001 and 0.01 mSv. The average Australian receives about 1.7 mSv a year from natural background radiation, so the scan is comparable to one or two days of normal life. |
| Results | A printed report, usually on the day. Dr Kumar goes through it with you. |
How to prepare
- Avoid strenuous exercise on the day of the scan.
- Avoid a large meal or a large amount of fluid in the two to three hours beforehand.
- If the scan includes bone density, do not take calcium supplements for 24 hours beforehand.
- Tell the provider if you have had a barium study, CT contrast or a nuclear medicine scan in the past week, as these can affect the result.
- Tell the provider if you are or may be pregnant.
- For a repeat scan, keep the conditions the same: similar time of day, similar meal and fluid, no hard training beforehand.
Larger body sizes
Most DEXA tables take patients up to about 200 kg. If your body is wider than the scan area, the provider can scan one side and calculate the whole-body result from it. This half-body method has been shown to be reliable. Let Dr Kumar’s team know if you are concerned, and they will check with the provider before you book.
Where it fits in your preparation
- Second consultation. Dr Kumar’s nurses introduce the dietitian and arrange your DEXA scan. Dr Kumar’s team sends the referrals for you.
- The scan. You book it with the provider at a time that suits you.
- Third consultation. Dr Kumar reviews your DEXA results with you, alongside your blood tests and your progress with the dietitian, and confirms the plan and timing for surgery.
- Repeat where needed. If there is a question about whether your composition is still changing, a second scan settles it.
The scan matters most where weight has come off quickly, whether after bariatric surgery or with weight-loss medication. Body contouring after weight-loss injections. Nutrition before skin removal surgery.
What it costs
- Expect to pay about $80 to $160 for a DEXA body composition scan at Sydney providers. Packages that add a consultation with an exercise physiologist or dietitian cost more. Dr Kumar’s team will tell you the current fee for the provider you are referred to.
- There is no Medicare rebate for a body composition scan. Medicare covers DEXA only for bone density, under specific criteria (items 12306, 12312, 12315, 12320, 12321 and 12322). Examples include confirmed low bone density after a minimal-trauma fracture, or a proven malabsorptive condition. If your GP has a separate reason to check your bone density, that test may be rebated under its own criteria.
- Health funds generally do not cover body composition scans. Some extras policies may contribute, so check with your fund.
For most patients, the scan is one of the smallest costs of preparing for surgery and one of the most informative. Costs of surgery with Dr Kumar.
Common questions
Do I have to have a DEXA scan? Dr Kumar asks every patient preparing for body contouring to have one, because it changes how preparation is planned. If there is a reason you cannot have one, discuss it with Dr Kumar’s team.
Will it change my operation? Sometimes it changes the timing more than the operation itself. A low muscle result usually means a period of focused nutrition and training before surgery is booked.
I already had a DEXA scan with my bariatric team. Can I use it? Bring it to your consultation. A recent scan may be enough, though a new one is often needed if your weight or training has changed since.
Can I have a DEXA scan in Orange or Penrith? DEXA body composition scans are available in many regional centres. Dr Kumar’s team will refer you to a provider convenient to you. Information for travelling patients.
Is the scan safe to repeat? Yes. The dose is very low, which is why it is used to track change over time.
Next step
If you are considering body contouring after weight loss, start with a consultation. A GP referral is required to see Dr Kumar. He consults at Westmead, Penrith and Orange. Call 1300 267 726 or book a consultation.
The initial consultation with Dr Kumar is $400, with a Medicare rebate of approximately $88 where you have a GP referral. Surgical fees are quoted individually after your consultation, in a written itemised quote. Body contouring after major weight loss.
All surgery carries risks, and individual results will vary. Read more about the risks of surgery here. A GP referral is required to see Dr Kumar.
Dr Rohit Kumar (MED0001630444) Registered medical practitioner, specialist plastic surgeon (specialist registration in surgery – plastic surgery).
