Metabolic Flexibility During Perimenopause: What It Means for Your Metabolic Health

Your body is constantly adapting to the fuel available to it.

After you eat, glucose becomes an important source of energy. Between meals and during certain types of activity, your body can draw more heavily on stored fat. During exercise, your muscles adjust their fuel use depending on the intensity and duration of the activity.

This ability to adapt between different fuel sources is known as metabolic flexibility.

And while it is a normal part of how the body regulates energy, metabolic health can change during midlife and the menopausal transition. Changes in oestrogen, body composition, physical activity, sleep and insulin sensitivity can all influence how your body uses and stores energy.

The good news is that these changes are not simply something you have to accept.

Understanding your metabolic health can help you make more informed decisions about movement, nutrition, sleep and your overall health during perimenopause and menopause.

What is Metabolic Flexibility?

Metabolic flexibility describes the body's ability to adapt how it produces and uses energy according to what you have eaten and what your body is doing.

For example, after a meal, your body has access to glucose from the food you've eaten. When you are between meals or exercising at a lower intensity, your body can increase its use of stored fat.

The balance between these fuel sources is influenced by several systems, including your muscles, liver, adipose tissue and hormones.

Insulin sensitivity is also an important part of this picture. When your cells respond appropriately to insulin, glucose can move from your bloodstream into your cells where it can be used or stored.

Metabolic flexibility is therefore not simply about "burning fat".

It is about your body's ability to adapt to changing energy demands.

Why Can This Change During Perimenopause?

The menopausal transition brings significant hormonal and physiological changes.

As ovarian hormone patterns change, there can also be changes in body composition, fat distribution, energy expenditure and glucose metabolism. Research suggests that fat oxidation and some aspects of metabolic flexibility may decline during the menopausal transition, although this is an evolving area of research.

At the same time, many women experience changes in sleep, stress, physical activity, appetite and muscle mass.

These factors can overlap.

For example, disrupted sleep may make it harder to maintain regular physical activity. Reduced activity can contribute to loss of muscle mass and changes in insulin sensitivity. Changes in body composition can then influence metabolic health further.

This is one reason I don't like looking at menopause through the lens of one hormone or one symptom.

Your metabolic health is influenced by the whole picture.

What Might You Notice?

There isn't one symptom that tells you that you have "lost" metabolic flexibility.

Feeling hungry between meals, afternoon fatigue, difficulty changing body composition or changes in exercise tolerance can have many possible causes. They shouldn't automatically be interpreted as evidence of metabolic inflexibility.

However, if you're noticing that your energy, appetite, body composition or exercise tolerance has changed during perimenopause, it can be worth looking at what's happening more broadly.

This may include considering:

• your blood glucose and insulin sensitivity
• cholesterol and triglycerides
• blood pressure
• body composition and waist circumference
• muscle strength and physical activity
• sleep quality
• nutrition
• stress and wellbeing
• medications and other health conditions
• where you are in your menopausal transition

Rather than asking, "Why can't my body burn fat anymore?", a better question may be:

What is happening with my metabolic health, and what can I do to support it?

How Can Metabolic Health Be Assessed?

There isn't a single routine test that tells you whether you are metabolically flexible.

Instead, your clinician may look at a combination of health markers depending on your individual circumstances.

These can include blood glucose, HbA1c, lipid levels, blood pressure and, in some circumstances, fasting insulin or other assessments of insulin resistance.

Your personal and family history also matters.

For example, having a history of gestational diabetes, type 2 diabetes, cardiovascular disease or other metabolic risk factors may change how your health is assessed.

Continuous glucose monitors can provide information about glucose patterns, but they are not a standalone test for metabolic flexibility or insulin resistance. A rise and fall in glucose after eating does not, on its own, tell us that your body is failing to switch from glucose to fat.

This is where personalised assessment matters.

What Actually Supports Metabolic Flexibility?

You don't need to follow an extreme diet or spend your life trying to stay in a "fat-burning zone".

Many of the foundations of good metabolic health are also the foundations of good health during menopause.

1. Build and Maintain Muscle

Resistance training is particularly valuable during midlife. Muscle is an important site for glucose uptake, and maintaining muscle mass can support insulin sensitivity, strength and physical function as we age.

You don't need to become a bodybuilder. Regular resistance exercise that is appropriate for your fitness level can make a meaningful difference.

2. Include Aerobic Activity

Walking, cycling, swimming, jogging or other forms of aerobic exercise can support cardiovascular fitness and metabolic health. There is also evidence that structured exercise can improve insulin sensitivity in postmenopausal women.

You don't need to rely solely on one type of training. A combination of aerobic activity and resistance training can provide different benefits.

3. Don't Underestimate Everyday Movement

Exercise is important, but so is what you do between workouts. Regular walking, taking the stairs, moving throughout the day and breaking up long periods of sitting can all contribute to your overall activity levels.

A short walk after a meal can be a simple way to add movement into your day.

4. Prioritise Nutritious, Satisfying Meals

There is no single menopause diet that everyone needs to follow. A balanced eating pattern that includes vegetables, fruit, wholegrains, legumes, lean protein, healthy fats and adequate fibre can support overall metabolic and cardiovascular health.

Protein is particularly important during midlife because maintaining muscle becomes increasingly important as we age. Rather than focusing on eliminating carbohydrates or constantly trying to keep insulin low, think about the quality and balance of your overall eating pattern.

5. Look After Your Sleep

Sleep can become more difficult during perimenopause, particularly when night sweats, hot flushes, anxiety or changing sleep patterns are involved. Poor sleep can affect appetite, energy, mood and metabolic health.

If your sleep has changed significantly, it is worth addressing the reason rather than simply trying to push through the fatigue. Sometimes treating the underlying menopause symptoms can be an important part of improving your overall wellbeing.

6. Pay attention to stress

Stress is another piece of the metabolic picture. Your stress response is designed to help you respond to short-term challenges. Ongoing stress, however, can affect sleep, appetite, activity levels and overall wellbeing.

You don't need to eliminate stress from your life. Simple strategies such as regular movement, time outdoors, breathing exercises, social connection and realistic boundaries around work and rest can all support your wellbeing.

What About Zone 2 Training?

You may have heard a lot about Zone 2 exercise recently.

Zone 2 generally refers to lower-intensity aerobic exercise where you can maintain a conversation while exercising.

It can be a useful form of cardiovascular training and can contribute to your overall fitness and metabolic health.

But it isn't a magic solution for metabolic flexibility.

You don't need to spend hours doing Zone 2 sessions to improve your health. The most useful exercise programme is one that is appropriate for your current fitness level, enjoyable enough to maintain and balanced with resistance training and other forms of movement.

Do You Need to Fast to Improve Metabolic Flexibility?

Not necessarily.

There is a lot of discussion around fasting and "metabolic switching", but fasting isn't essential for good metabolic health and isn't appropriate for everyone.

For some people, structured meal timing may be useful. For others, particularly those with certain medical conditions, medications or a history of disordered eating, fasting may not be appropriate.

Rather than following a fasting protocol because it is trending online, it's worth asking what approach is sustainable and appropriate for your health.

Metabolic Health is About Much More Than Body Weight

This is particularly important during perimenopause.

Changes in body composition can occur during the menopausal transition, including changes in fat distribution and loss of lean mass. These changes can affect metabolic and cardiovascular health even when the number on the scales hasn't changed dramatically.

So instead of focusing only on weight, we can look at the bigger picture:

• How is your blood pressure?
• What are your glucose and cholesterol levels?
• Are you maintaining muscle and strength?
• How well are you sleeping?
• How active are you?
• How are you feeling?
• And what are your longer-term health risks?
• These questions give us much more useful information than the scales alone.

You Don't Need to "Fix" Your Metabolism

If your body feels different in your 40s and 50s, that doesn't mean you've broken your metabolism.

Your body is adapting to a new stage of life.

The goal isn't to force your body into constantly burning fat or to find the perfect metabolic hack.

It's about supporting your metabolic health through sustainable habits and, when appropriate, identifying health issues that may need further assessment or treatment.

Exercise, resistance training, nutritious food, good sleep and regular health checks all have an important role to play. Australian health guidance also recommends staying active through aerobic, resistance and weight-bearing exercise during and after menopause.

And sometimes, there is more to investigate.

If you're experiencing changes in your energy, body composition, sleep, appetite or exercise tolerance during perimenopause, you don't have to work it out on your own.

Looking at the Whole Picture

Metabolic health during perimenopause isn't about finding one missing piece.

It's about understanding how your hormones, muscles, nutrition, movement, sleep, stress and existing health conditions may be interacting.

That is why personalised care matters.

If you're noticing changes in your body or metabolism during perimenopause or menopause, a consultation can help you understand what may be contributing to those changes and which areas are worth exploring further.

Book a consultation today to explore your symptoms, metabolic health and personalised options for supporting your wellbeing through midlife.