BMI for weight loss surgery
Is BMI really the best way to decide if weight loss surgery is for you?
Let’s talk about BMI. You’ve probably heard it thrown around a lot when it comes to weight and health. But what does it really mean, and how much should you rely on it when thinking about something like weight loss surgery?
- Jon Armstrong
In this video, Perth-based Bariatric Surgeon Mr Jon Armstrong talks about BMI and whether BMI is an accurate tool for bariatric surgery. Follow us on Instagram for more reels!
What is BMI?
BMI stands for Body Mass Index. It’s just a simple calculation: your weight in kilograms divided by your height in metres squared. That’s it. It’s been used for years to figure out whether someone is in a “healthy weight range.” Traditionally, a BMI over 35 or 40 was a sign that you might benefit from weight loss surgery because it could mean you’re at higher risk of health problems down the track.
But here’s the thing—BMI is not perfect. It doesn’t tell the full story about your health.
Why BMI isn’t always accurate
BMI doesn’t know the difference between muscle and fat. Let’s say you’re a rugby player with loads of muscle. You could have a BMI of 40, but that doesn’t mean you need weight loss surgery—you’re just strong – you might not have a lot of fat. On the other hand, someone with a “normal” BMI could still have too much of the unhealthy kind of fat, called visceral fat, and be at risk for serious health problems.
So, BMI might give a rough idea, but it’s not the whole picture. There’s so much more to consider.
What matters as well?
When deciding if weight loss surgery might be right for you, we look at lots of things, not just BMI. The most important questions are about your health and how much risk you’re carrying for the future. Things like:
Do you have type 2 diabetes?
Is your blood pressure high?
Are your joints struggling to cope with your weight?
Do you have fertility issues, PCOS, or high cholesterol?
These are the kinds of problems that can improve massively after weight loss surgery. It’s about looking at the bigger picture, not just a single number.
A better way to measure fat and muscle
If you’re really curious about your body composition—how much fat vs muscle you have—a DEXA scan or body composition scan can give a much clearer answer. These scans are far more accurate than BMI and can help us understand what’s really going on in your body.
Don’t get too hung up on BMI
At the end of the day, BMI is just a piece of the puzzle. It’s a starting point, not the whole story. If you’re thinking about weight loss surgery, the best thing you can do is make an appointment so I can look at your overall health, your lifestyle, and your future risks.
Got questions? Feel unsure about your BMI or what it means for you? Don’t worry—you’re not alone, and we’re here to help. Reach out anytime for a chat.
