Last week I wrote about my weight loss struggles, and my first appointments with a naturopath and functional doctor…

Exactly how overweight am I?

As I spoke about in my first post, my weight has not budged within a 3kg range since 2010, despite following a paleo diet and exercising regularly. Everyone always tells you that muscle weighs more than fat, but does it really? Does this apply to me?

I’ve been going to the gym regularly for the last few years, and for the last year or so I’ve been doing CrossFit. My arms have distinct muscle in them that I swear didn’t used to be there, and I am making good progress on increasing the weight I can lift – so that would suggest I have more muscle than I used to. So if I do have more muscle, and it weighs more, how can my total weight still be EXACTLY THE SAME?

The naturopath had suggested I go and have a DXA (Dual-energy X-ray absorptiometry; formally called a DEXA scan) body scan performed so I could see exactly what my body composition is. I was initially quite wary about the radiation, but apparently it’s the same dose of radiation as a short flight between Sydney and Melbourne. I take domestic flights often, this is important, so I figured it was worth it.

The DXA scan

Have you had one of these body scans? It’s completely open (I was expecting it to be enclosed, like an MRI scan) and not unlike being photocopied (I’d imagine). You lie on the DXA machine and it whizzes over you for about ten minutes whilst you watch an image of your body appear on the screen on the ceiling. I found it really confronting. Your fat mass is displayed in yellow. Lying flat on your back, no tailoring can disguise the yellow fat shown in the image.

I’m not ready to post my scan images just yet – it was enough to convince myself just to write about my weight loss struggle, let me tell you! The images in this post show some example DXA scans I found online. When I go back for my follow up scan in a few months, I will post both scans, side by side to show the difference and all of the statistics that go with it.

The image shows your bone in blue and your lean body mass (i.e. muscle & vital organs) in red. What amazed me was my skeleton. It is small – the “I’m just big boned” excuse can be completely dismissed. And how much would you expect your skeleton to weigh? Well mine is just over 2.2 kilos. Incredible. These DXA scans are also used to look at bone density, so I was pleased to see my bone mineral density is excellent (note to all those who’ve been told paleo doesn’t give your body enough calcium!). I also had slight variances between my left and right side, with my right side weighing fractionally more. Interesting – I wonder if many people have exactly the same on both sides?

In terms of muscle mass, the physiologist who conducted my DXA scan, and talked me through the results was surprised by how much muscle mass I have. He seemed to think I have about 10kg more muscle than an “average” woman of my weight and height would have. This was great to hear – and also surely must mean that I have in fact lost fat – it must just be a coincidence that my total weight number has not changed…

Unsurprisingly, my fat mass was too high – but only about 6% above a healthy range (I expected it to be a lot worse than this). The DXA scan clearly showed what I already knew, I store my fat around my hips (a typical pear shape). The danger zone is storing fat around your middle (the “central abdominal zone”, so I’m glad that’s one risk factor I don’t have. My estimate had been that I needed to lose about 15kg of fat, but the actual measurements, suggest I may “only” need to lose 11.9kg. It’s still a lot, but thanks to the bonus lean muscle mass, less than I expected.

Metabolism

The scan also calculated my Resting Metabolic Rate, which has opened up a whole new avenue on my journey of discovery…. metabolism, it turns out, is absolutely crucial in weight loss.

The DXA scan measured my resting metabolic rate as 1639 kcal a day. That means just to exist with absolutely no physical activity, my body needs 1639 calories a day…

I’m going to talk a lot more about metabolism in my next weight loss post – and share with you what I’ve found out – and what it means.

Before then, please share your experiences below. Have you had a DXA body scan? What did you find out?