Weight-loss medications such as Wegovy are becoming increasingly common and, for many people, can result in significant weight loss. But when the number on the scales goes down, there is another important question to ask:
What are you actually losing – fat, muscle, or both?
In this discussion with registered clinical nutritionist Anastasia Bennett, Bone and Body Blueprint radiographer Heidi Richardson talks about what we are seeing through DXA body composition scans in our clients using weight-loss medications.
Weight loss doesn't always mean fat loss.
A set of bathroom scales can tell you how much your total body weight has changed, but it can't tell you where that change has come from.
Weight loss can include:
Body fat
Muscle mass
Other lean tissue
This is particularly important when weight is being lost quickly.
At Bone and Body Blueprint, we're seeing an increasing number of clients having a DXA body composition scan before starting weight-loss medication, followed by another scan three or six months later. This gives us something valuable to compare. Rather than simply seeing that someone has lost 10kg, we can see how much of that change has come from fat and how much has come from muscle.
What are we seeing in these DXA scans?
The results vary considerably from person to person, and we are seeing considerable variation in the proportion of fat vs muscle lost.
In some of the clients we have scanned while using weight-loss injections, up to approximately 50% of the weight lost has been lean or muscle mass.
This isn't what happens to everyone, and it isn't a figure that should be applied to everybody taking weight-loss medication. It is simply something we are seeing in some of the before-and-after DXA scans coming through our clinics.
And it highlights why looking at body composition – rather than weight alone - is useful.
Why is maintaining muscle important?
Muscle mass is important throughout life. Preserving muscle becomes increasingly important as we age.
This is particularly relevant for women approaching and moving through perimenopause and menopause, when maintaining muscle can already require more attention.
Simply losing weight isn't necessarily the whole goal. Ideally, you want to understand whether your approach is helping you reduce body fat while retaining as much valuable muscle as possible.
Nutrition and strength training still matter.
We have noticed that clients who are also working with a nutritionist, personal trainer or other health professional often have a better understanding of what they need to do while losing weight.
That can include paying attention to areas such as:
Adequate nutrition.
Protein intake.
Strength and resistance training.
Recovery.
Maintaining healthy habits while weight is coming off.
Weight-loss medication may affect appetite and how much you're eating, but maintaining muscle requires a deliberate approach. Working with appropriate health and fitness professionals can help you understand what your individual body needs.
Why have a DXA scan before starting weight-loss medication?
If possible, having a body composition scan before you start gives you a baseline. A DXA scan measures much more than your total body weight. It provides information about your:
Total body fat.
Lean mass.
Muscle distribution.
Visceral fat.
Body fat percentage.
Changes between different areas of the body.
You can then repeat your scan later and compare the results.
For example, instead of knowing only that you've lost 8kg, you can see how much fat and lean mass have changed and where those changes have occurred.
Without a baseline scan, we can still provide valuable information about your current body composition – but we don't have the same before-and-after comparison.
How often should you repeat your body composition scan?
There is no one schedule that suits everybody. For clients using weight-loss medication, we are commonly seeing follow-up scans around three to six months after their initial scan.
The right timing will depend on your individual situation, rate of weight loss and health goals. The purpose isn't simply to see whether you've lost more weight. It is to assess how your body composition is changing.
If muscle mass is declining more than expected, having that information gives you an opportunity to discuss your nutrition, exercise and overall approach with the appropriate health professionals.
What about bone density?
Bone health is also an important consideration when losing weight, particularly where significant dietary or nutritional changes are involved. However, changes in bone density generally occur much more gradually than the body composition changes we can see over a few months.
For that reason, our immediate focus when following clients using weight-loss medication is often on changes in fat and muscle mass. Bone density is something that may be considered over a longer period, depending on your individual health, risk factors and clinical circumstances.
More information means better informed decisions.
One of the biggest benefits of a DXA body composition scan is simply having objective information about your own body.
If you're considering weight-loss medication, already using it, or working through a significant weight-loss programme, a body composition scan can provide a useful baseline and help you track your progress over time.
DXA body composition scans in Te Awamutu and Pukekohe
Bone and Body Blueprint provides DXA body composition scanning from our clinics in Te Awamutu and Pukekohe. We'll take you through your results so you understand what the numbers mean for you.
If you're using weight-loss medication and want to understand whether you're losing fat or muscle, a DXA body composition scan can give you information that your bathroom scales simply can't provide.
