Medications based on GLP-1 or GLP-1/GIP have changed the treatment of obesity and type 2 diabetes. Where indicated, they can support significant weight loss. The scales show how many kilograms have been lost – but not what that weight loss consists of.
What studies on body composition show
In the large trials that led to approval, body composition was measured by DEXA in subgroups. On average, fat mass decreased more than lean mass. At the same time, however, lean mass can also decline. How much this applies to any individual cannot be deduced from study averages – it depends, among other things, on starting weight, age, diet, physical activity and the pace of weight loss.
Lean mass is not the same as muscle mass
As well as skeletal muscle, “lean” or fat-free mass includes organs, connective tissue and body water. It is therefore an approximation of muscle mass, not a direct measurement. Muscle strength is not recorded in a DEXA scan.
Why preserving muscle matters
Muscle strength and muscle mass contribute to mobility, stability and independence – especially in older age. A progressive loss of muscle strength and muscle mass is known as sarcopenia; diagnosing it requires a medical assessment that checks strength above all, as well as muscle quantity.
What a DEXA body composition scan measures
- Fat mass and body fat percentage
- Lean soft tissue mass as an approximation of muscle mass, broken down for arms, legs and trunk
- Bone mineral content (a bone density scan to assess osteoporosis is a separate examination)
Baseline scan and follow-up monitoring
A scan at the start of treatment records a baseline value – the reference point for later comparisons. A follow-up scan is often carried out after several months; agree the right interval with your treating doctor. A further scan after stopping treatment can also document the course.
What the scan does not do
- DEXA does not decide whether to start, adjust the dose of, or stop a medication.
- The scan does not replace medical care or nutritional counselling.
- Any changes to treatment are made solely by your treating doctor.
At Röntgen am Kai, the body composition scan is a private service that can be booked without a referral; please allow around 20 minutes.