It's Not Just Fatigue: What's Really Happening To Your Energy And Metabolism In Perimenopause

There's a specific kind of tiredness many women describe in their late thirties, forties and early fifties. It's not just fatigue; it's the sense that, in the simplest terms, everything has become less efficient. The same habits that once kept us stable, training, eating well, the odd cleanse, now deliver a smaller return, and we need to do increasingly more just to tread water.

In clinic and in conversation, this is one of the most common patterns I see. Most of the time, it's because our underlying physiology has changed and we haven't been taught to change with it. The main challenge is that modern life continually draws on the same finite reserve, and for many women it peaks in perimenopause, when shifting hormones reduce adaptability and resilience at precisely the moment when career and family demands are at their highest. What we used to push through easily suddenly feels disproportionately hard, and we jump to the conclusion that this is simply our new normal.

Why so many women are tired, even when they're doing everything right

When people think of metabolism, it's often through the lens of weight. But metabolic health is all-encompassing. Simply put, it's how we create and process energy. It is not a single lever but a complex energy system made up of how efficiently cellular energy is produced, how intelligently the body allocates it under pressure, and how stable the network of hormones remains while all of that is happening. In perimenopause, this is the system that loses the most bandwidth, and it happens quickly.

Energy is created at a cellular level. Every second, our cells convert nutrients into a useable form of energy called ATP, which powers almost everything we do: brain function, mood regulation, movement, digestion, immunity, repair, sleep and hormone signalling. When energy production is robust, we can absorb stress, maintain hormonal rhythm and recover in the background. When it is constrained, smaller stressors hit harder, hormone shifts feel more pronounced and it takes longer to recover from the same things we used to bounce back from naturally.

The female energy loop: metabolism, stress and hormones

One of the biggest reasons women feel stuck is that energy, stress and hormones get treated as separate problems, when in reality they are all part of the same feedback loop. You cannot address hormones without looking at the physiology of the stress response, and it's hard to stabilise stress physiology without looking at the energy system that underpins it. Your metabolism creates energy, stress signalling decides where that energy goes, and hormone output reflects the downstream consequences. The body is one interconnected system, and it helps enormously to start treating it as one.

Understanding hormone changes in perimenopause

Perimenopause is defined by hormonal volatility: fluctuating levels of oestradiol and progesterone followed by a steady decline. Because oestrogen has wide-reaching effects across the brain, immunity and energy metabolism, symptoms are broad and touch virtually every aspect of wellbeing. Here are some of the most important things to understand about oestrogen.

It impacts cellular energy. Oestrogen helps regulate our mitochondria, the sites where most ATP is produced. As oestrogen declines, our ability to produce energy efficiently follows suit.

It influences inflammation. Oestrogen has modulatory effects on inflammation and neuroinflammation. As levels decline, inflammation can rise, creating more internal stress, worsening fatigue and influencing pain sensitivity and recovery.

It supports the brain. Hormonal fluctuations affect the central nervous system and are linked to a higher risk of mood disturbances, including depressive symptoms, as well as brain fog and difficulties with memory recall.

It drives an efficient metabolism. Oestrogen helps us build muscle and keeps us more sensitive to insulin. As levels fall, insulin resistance can increase and building muscle becomes more difficult.

Layer onto this the fact that many of us are missing foundational support we don't even realise we need.

95% of women in the UK don't consume enough dietary fibre. Fibre plays a critical role in cortisol and stress management: it modulates the gut-brain axis, reduces systemic inflammation, is essential in oestrogen metabolism and helps stabilise blood sugar. Women also tend to either undereat or mistime their protein, often due to over-fasting, low-calorie diets and a tendency towards more plant-based eating. One in six women in the UK drinks more than the recommended weekly limit of alcohol, and even a few drinks a week can impact hormone health, inflammation, cancer risk and the stress response. The average adult in the UK consumes 700g of sugar per week, more than 230% of the recommended maximum, with 65% of that coming from ultra-processed foods. And finally, only 4% of women in the UK meet strength training guidelines, meaning most are not building or maintaining enough muscle, one of the most important metabolic organs for energy, blood sugar regulation and long-term resilience.

This list can feel overwhelming, but the key is not to change everything at once. A long-term mindset is far more effective. Start with a gentle audit of what you eat, your habits and your exercise routine, then make targeted changes you can sustain, building gradually over time. As your metabolism becomes more robust, you will start to feel your capacity increase. What looks daunting now will create more flexibility, energy and ease in the long run.

Here's what to focus on to support the system as a whole

Consistent, adequate nutrition. Protein and fibre become more important in this life stage. Aim for sufficient overall energy intake to match demand, with protein at around 1.2g per kg of ideal body weight per day.

Better-quality inputs most days. Less reliance on ultra-processed food and alcohol as a coping mechanism, more focus on whole foods.

Progressive strength training. To build and protect muscle, improve glucose handling and increase metabolic reserve.

Real recovery. Sleep protection, nervous system regulation and avoiding the trap of stacking high-intensity exercise on top of an already high-stress life.

Supplementation in perimenopause

Perimenopause is one of the life stages where targeted supplementation can make a meaningful difference. These are my top recommendations.

The Perimenopause Support Set. This contains Enhanced NAD+ Complex for mitochondrial support, mood support and hormonal adaptogens; Essential Creatine for muscle health, recovery and energy production; and Metabolic Fix to support blood sugar, cravings and gut health.

Essential Fibre. If you're struggling to hit your fibre goals (a minimum of 30g per day), or find high-fibre foods difficult to tolerate due to IBS or bloating, this low-FODMAP fibre supplement supports gut health, regularity, appetite and blood sugar.

Taking a holistic approach to perimenopause and metabolism means supporting energy production, managing stress load and prioritising recovery. In doing so, hormonal changes become less disruptive and far more manageable.