DEXA — Take 2

The Wins and the WTFs after a year of training

TLDR

A year after my first DEXA scan, I’ve reduced both overall fat and visceral fat, and maintained strong bone density—two clear wins for long-term health.

But my Lean Mass Index (a proxy for muscle) declined, despite a year of dedicated strength training. I’ve uncovered a few possible explanations, including postpartum changes, my training approach, protein intake, and even the possibility of perimenopause. I’m retesting in 6 months and recalibrating my training and nutrition to aim for gains in muscle mass.

👉 Please subscribe, comment, share or ❤️ so more people can discover Extend on Substack 🙏

First anniversary retest

Just like that, a year passed since my first DEXA scan—and it was time to retest.

I was excited.

I’d committed to strength training all year, and I was looking forward to seeing the payoff in the form of a higher lean mass index (LMI)—a signal I’d gained muscle.

On that front, I was sorely disappointed. My LMI had gone backwards, not up. WTF! And why?

On the other hand, the results for fat, visceral fat, and bone density showed encouraging progress towards my goal of living healthier for longer.

A quick DEXA refresher

A DEXA scan is the gold standard for measuring body composition. It tells you how much fat, muscle (as part of lean mass), and bone you’re carrying—essential information for tracking towards healthspan. I wrote more about it in this earlier Extend.

A year ago, I had my first DEXA scan to establish baselines across fat mass, visceral fat, bone density, and lean mass. After a year of (mostly) following my own health advice, here’s what my one-year follow-up scan revealed:

Fat Mass

DEXA provides multiple fat metrics, but two stand out for tracking meaningful change:

• Fat Mass Index (FMI): Fat mass adjusted for height, allowing us to see fat changes independent of muscle gain or loss.

• Visceral Fat Area: The amount of fat surrounding vital organs like the heart, liver, and lungs.

My FMI dropped 9%, from 6 to 5.4.

My visceral fat area dropped 16%, from 36 cm² to 30 cm².

I was especially happy with the visceral fat reduction. Visceral fat, more than the fat under our skin, is linked to diseases like type 2 diabetes, heart disease, colon cancer, and stroke. Lowering this is a win for metabolic health.

Bone Density

Bone mineral density (BMD) is a marker of overall health and an important factor in reducing osteoporosis risk—especially for women, who are four times more likely to suffer from it.

My z-score improved 10%, from 1.0 to 1.1.

That’s a small change, and not statistically significant—BMD generally shifts slowly. But it still felt good to see movement in the right direction. Weight-bearing and high-impact exercise are among the best ways to maintain and improve bone density, so I’m chalking this up as a small reward for consistency.

Lean Mass Index (LMI) — aka Muscle

LMI is the best proxy DEXA offers for muscle mass. It measures lean mass (muscle, organs, ligaments, connective tissue) relative to height. While you can’t directly measure muscle alone, shifts in lean mass typically reflect changes in muscle.

I’d hoped to improve my LMI from the 42nd percentile (LMI of 15). Instead, my LMI declined to 14.1, dropping me to the 31st percentile—a 3 kg or 6% decrease.

I was surprised and disappointed. This was the first year I’d consistently committed to weight training, and I genuinely feel stronger. Something didn’t add up.

Why Did My LMI Drop?

Here are the factors I’ve considered:

1. Insufficient training stimulus

   Perhaps my training wasn’t progressive or intense enough, or I wasn’t consistently supporting it with adequate protein, leading to an actual loss in muscle.

2. Post-Pregnancy and Breastfeeding Effects

   My baseline scan was just 3 months postpartum while I was still exclusively breastfeeding. I’ve since learned that postpartum fluid retention and breast tissue changes can inflate lean mass by up to 3 kg at 3 months postpartum—which could entirely account for the difference.

3. Muscle Definition vs Muscle Mass

   I’ve noticed more muscle definition and feel stronger—plus, my formerly puny arms are getting compliments! But I’m now reflecting on whether fat loss, rather than muscle gain, is driving the appearance of definition.

4. DEXA Precision Error

   DEXA is reliable but not perfect. Measurement error can account for up to a 1.5% variance in lean mass—enough to explain part of the change.

5. Perimenopause

   I don’t know if I’ve entered perimenopause, but at my age, it’s possible. Hormonal shifts could contribute to muscle loss—so the DEXA results make me keen to learn more here.

So—Have I Lost Muscle?

I really can’t say, one way or the other. But here’s what my instincts tell me:

• My baseline LMI was inflated by postpartum and breastfeeding factors.

• My training and nutrition over the year have been helpful but aren’t dialled in as well as I thought.

Where to From Here?

First, a moment to celebrate: my bone density and visceral fat trends are moving in the right direction—key wins for healthspan.

Next, the plan:

• Retest in 6 months: With postpartum effects behind me, I’ll get a clearer, apples-to-apples comparison.

• Refresh my strength training protocol: I’m planning to lift heavier, adopt an upper/lower body split, and allow better recovery between sessions.

• Prioritise protein: My intake has been dipping below target—time to correct that.

Once again, this experience has reminded me that progress in healthspan isn’t always linear—or obvious. Our bodies are complex, and so many variables are at play. But overall, my follow-up DEXA shows I’m making meaningful progress and has given me guidance on where to concentrate next. And just like I planned to, I’ll continue to learn and refine as I go.

xx

Toni

👉 Please subscribe, comment, share or ❤️ so more people can discover Extend on Substack 🙏