By Daniëlle van der Leest | Women’s Strength & Wellbeing Coach | Founder of ActiveWomen | Mum of 3
A client came to me this week — 40-something, strong, training consistently, doing everything she thought she was supposed to be doing. She’d been tracking her food, keeping her calories low, and the scale had moved. But in her last few sessions she felt weaker, not stronger. Her muscle mass was trending down. And she was frustrated, because she was showing up.
She’d put herself on roughly 1400 calories a day — sometimes less, deliberately, to “bank” for higher-calorie days later in the week. She was hitting over 100g of protein. On paper, it looked like discipline. In her body, it was telling a different story.
This scenario is so common I want to write it here, because I know she’s not the only one.
The problem isn’t your effort. It’s the maths.
When your body doesn’t get enough total calories, it goes into what I call conserve mode. It prioritises keeping you alive and functioning — your heart beating, your brain working, your organs running — over building new muscle tissue. That’s not a flaw. That’s your body being very good at its job.
So even when protein intake is excellent, if total calories are too low, your body simply doesn’t have the surplus resources to build and maintain muscle. It starts using what it has. And what it has includes muscle tissue.
This is why she was losing weight — but losing muscle alongside fat. The scale went down, but not in the way she wanted.
The BMR problem nobody explains
BMR stands for Basal Metabolic Rate — the calories your body burns just existing, before any movement, exercise, or daily activity. For most active women in their 40s, this is somewhere between 1400–1600kcal depending on height, weight, and body composition.
If you’re eating at or below your BMR on several days of the week, your body has no buffer. Every step you take, every session you do, every load of laundry you carry — it’s all coming from resources your body was already using just to function.
Training hard on top of that doesn’t build muscle. It depletes it.
Why calorie banking backfires
My client was eating 1079kcal on Wednesday — intentionally — because she knew Thursday and Saturday would be higher. She was trying to average out at around 1500kcal per day across the week.
The logic makes sense on a spreadsheet. But your body doesn’t run on weekly averages. It runs on what’s available today.
On that 1079kcal Wednesday, her body was under-fuelled. It responded accordingly — conserving, protecting, not building. No amount of higher-calorie days later in the week fully undoes that signal. The swing from very low to higher actually makes things harder, because your body becomes less predictable, not more efficient.
Consistent, moderate fuelling — slightly more than you think you need, every day — protects muscle far better than averaging it out across the week.
The training side of the equation
Here’s something most women don’t know: when you work a muscle, it stays in repair and build mode for roughly 24–48 hours. After that, the signal fades.
If you’re training twice a week — which is what many busy women manage, and that’s genuinely not nothing — there are days in between where your muscles are getting zero stimulus to grow or even maintain. Under normal fuelling, your body holds onto muscle anyway. But when you’re also under-eating, those quiet days become a problem. Your body looks for fuel. Muscle is available.
Adding even one short extra session — 30 minutes, light, at home — between your main sessions doesn’t need to be intense. It just needs to remind your muscles they’re needed. That signal, when calories are lower, is what tips the balance from breakdown toward maintenance.
So can you lose fat AND gain muscle?
Yes — and this is called body recomposition. It absolutely happens, especially for women who are relatively new to consistent strength training or returning after a break. But it requires two things that are often in direct conflict with each other:
A reason for the muscle to grow — progressive overload. You have to consistently challenge the muscle with more than it’s used to: more weight, more reps, more range of motion, or less rest. If you’re doing the same session week after week, your body has no reason to adapt.
Resources for the muscle to grow — enough calories and protein. You cannot build something from nothing. Muscle is metabolically expensive. Your body will only invest in it if there’s enough fuel to justify the build.
The mistake most women make is prioritising the fat loss so hard that they remove the very conditions muscle needs to grow. They end up lighter but softer, weaker but smaller — which is almost never what they actually wanted.
What actually helps
None of this requires a dramatic overhaul. For my client, the starting point was small and specific:
- Bring calories up slightly — not to a surplus, but consistently above BMR, every day, rather than banking and swinging
- Keep protein high (she was already doing this brilliantly)
- Add one short home session between her main training days — not to exhaust herself, just to keep the muscle signal going
- Be patient with the recomposition timeline — it’s slower than pure fat loss, but the result is a body that’s actually stronger, not just lighter
The goal shifted from “lose weight fast” to “build a body that works.” That’s a different brief. And it requires different conditions.
The bigger picture
Showing up is not enough on its own — and that’s not a criticism, it’s just the truth. Showing up with too little fuel is like trying to build a house while someone quietly removes the bricks. The effort is real. The outcome won’t reflect it.
If you’ve been consistent, training hard, eating “well,” and still feeling like your body isn’t responding — look at your calories before you look at your effort. Chances are, you’re not doing too little. You’re fuelling too little.
Your body will build if you give it a reason and the resources. Both matter.
Want to understand how to fuel your training properly — across every stage of life?
My free Nutrition Guide covers exactly this: how to eat to support strength training, what changes through pregnancy, postpartum, and perimenopause, and how to stop letting under-fuelling get in the way of the results you’re actually working for.
→ Download the free Nutrition Guide
If this resonated and you want to go deeper — my book covers the full picture of strength training for women through every life phase, including the nutrition side that most training books skip entirely.
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Daniëlle van der Leest is a Women’s Strength & Wellbeing Coach, Founder of ActiveWomen, and Mum of 3. She specialises in strength training for women through pregnancy, postpartum, and perimenopause.
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