Why Your Metabolism Changes After 40 And What You Can Do About It
If you’re over 40, you may have noticed your metabolism isn’t what it used to be. You might feel constantly tired even though you “eat well,” find it harder to maintain muscle tone, or notice fat gathering in new places. The truth is, metabolism naturally changes as we age, partly due to hormonal shifts. But here’s the good news: there are ways to support it, restore energy, and reduce long-term risks like diabetes, cardiovascular disease, and cognitive decline.
What Is Metabolism—and How Does It Change After 40?
Metabolism isn’t just about calories or what the scales say. It’s the complex network of processes your body uses to convert food into energy. That includes digestion, absorption, and nutrient transport to your cells, as well as the cellular process that turns glucose into ATP ie the energy that powers every cell.
Metabolism also involves energy storage (glycogen in your liver, muscles, and fat cells) and regulation by your thyroid, which controls your basal metabolic rate and how efficiently your body burns fat and uses glucose.
After 40, many of these processes naturally slow down. That means the diet and exercise routine that worked in your 30s may no longer cut it.
Top Factors That Influence Metabolism After 40
Here’s what really impacts metabolism in middle age and how it differs between men and women.
1. Muscle Mass
As we age, muscle naturally declines. Resistance training and enough protein are crucial to slow this loss. Men tend to have more muscle, but women especially need to prioritise strength from peri menopause onwards. Aim for roughly 1.2 g of protein per kilogram of body weight, spread evenly across three main meals.
2. Thyroid Function
If you’re constantly tired or noticing unexplained weight changes, your thyroid could be a factor. Regular checks of TSH, fT3, and fT4 and even urinary iodine can help identify subclinical hypothyroidism, which is surprisingly common in Australian women.
3. Sleep Quality and Stress
Poor sleep isn’t just exhausting it slows metabolism. Disrupted sleep can increase ghrelin, the hunger hormone, while elevated cortisol from stress promotes fat storage, particularly around the middle. Sleep and stress management are essential for keeping energy and metabolism in check.
4. Hydration
Water is literally a metabolic catalyst. It’s needed for energy production in cells, fat breakdown (lipolysis), and nutrient delivery. Aim for 1.5–2 L per day, adjusting for hormonal cycles or muscle mass.
5. Hormonal Balance
From insulin to cortisol, oestrogen, progesterone, and testosterone, hormones influence nearly every aspect of metabolism. Quality nutrition, regular exercise, and stress management support metabolic processes. Targeted herbal and nutritional interventions can also help.
6. Environmental Temperature
Yes, your metabolism responds to temperature. Mild cold exposure can activate brown fat and increase calorie burn slightly. But it’s not one size fits all. If you have cardiovascular issues, thyroid problems, or high stress, approach ice baths or cold exposure cautiously. Start slow and listen to your body.
How a Naturopath Can Fine-Tune Your Metabolism
A naturopath doesn’t just treat symptoms we look for the root causes of low energy and metabolic changes. Ways we can help include –
• Tailoring diet and meal timing to support energy production and hormonal balance.
• Creating personalised exercise and resistance strategies and helping you stay on track. Accountability is everything !
• Supporting thyroid, adrenal and hormone balance through nutrition, lifestyle and safe herbal or nutrient interventions.
• Addressing hidden factors such as inflammation, poor gut health and nutrient deficiencies that can quietly slow metabolism.
The goal isn’t just weight management. It’s sustainable energy, vitality and feeling like yourself again and proactively caring for your health even as your body changes with age.
Takeaway
Metabolism naturally slows after 40 but it doesn’t have to mean inevitable weight gain, fatigue, or frustration. Understanding how age, hormones and lifestyle affect metabolism and taking strategic action now, can dramatically improve your energy, health, and body composition today and for decades to come.
If you have been struggling with poor energy, weight gain and want to know what’s driving your metabolism , book a consultation today. Together, we’ll create a plan tailored specifically for you that works.
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