3 mistakes that ruin your metabolism

If you've followed me for some time, you know that thyroid conditions are a bread (gluten free!) and butter of my business.

I take pride in my expertise in thyroid health, and love working with thyroid clients. But that's also how I know that for many women, suboptimal thyroid function means a whole bunch of problems with their weight and overall metabolism.

The most common type of clients I get through my doors is women who are really clued up in matters of health. They read a lot, they know what to do and are seemingly doing all the right things. 

Yet the needle is not moving. 🦹‍♂️

Until we sit down and I help them unpack what’s really going on and what changes are needed to get the process moving forward.

So today, I want to walk you through three common “healthy” habits that can quietly disrupt your thyroid and metabolism, and show you how to adapt them to truly support your body.

⛔ IGNORING NERVOUS SYSTEM REGULATION

Why it’s overlooked:
It’s not trendy. It doesn’t burn calories. And most wellness advice still treats stress as a mindset issue, not a biological one.

What goes wrong after 40:
By midlife, your nervous system has weathered decades of stress - work, family, emotional strain, trauma, even chronic dieting or overexercising. And that wear and tear adds up.

A constantly activated sympathetic nervous system (fight or flight) leads to:

•  Chronically elevated cortisol, which suppresses thyroid function and insulin sensitivity(=insulin resistance, =inflammation and weight gain around waistline)
•  Poor conversion of T4 to your active thyroid hormone T3 (=the body shifts into a “preserve and store” mode)
•  Digestive shutdown (bloating, reflux, sluggish motility)
•  Blood sugar dysregulation and inflammation (=water retention, for some people can be huge)
•  Disrupted sleep and recovery (=poor food choices next day)

The result? A metabolism that feels “stuck,” even when you're eating well and exercising.

What to do instead:
☑️ Build nervous system hygiene into your daily routine - not just self-care on Sundays
☑️ Practice 5–10 minutes of deep belly breathing, legs-up-the-wall, or vagus nerve activation each day
☑️ Prioritise quality sleep, ideally starting long before midnight, as this is when the nervous system resets
☑️ Create safe pauses during the day - real breaks, not just scrolling your phone between tasks

⛔ EXTENDED INTERMITTENT FASTING

Why it’s popular:
Fasting is praised for fat-burning, insulin sensitivity, and longevity. And those benefits are real - in the right context.

What goes wrong after 40:
As oestrogen, progesterone, and DHEA begin to decline, the female body becomes more sensitive to stress. Fasting beyond 14-16 hours can spike cortisol (your stress hormone), which:

•  Signals the body to conserve energy (=slowing your metabolism)
•  Suppresses T3, your active thyroid hormone (=the body shifts into a “preserve and store” mode)
•  Disrupts blood sugar balance(=may increase weight around midline)

What to do instead:
☑️ Stick to a 12–14 hour fast (e.g., 7pm–9am)

☑️ Avoid fasting on high-stress or poor-sleep days

☑️ Consider fasting between your meals instead

☑️ Break your fast with protein + healthy fat to nourish your adrenals and thyroid

☑️ Eat in a relaxed state only - digestion starts with calm. Do a couple of minutes of deep belly breathing before you touch the food on your plate. Done? Great, now tuck in.

⛔ LONGTERM LOW-CALORIE DIETS

Why it’s popular:
We’ve all been told: "Eat less, move more." It sounds simple. And in the short term, cutting calories can lead to weight loss.

What goes wrong after 40:
Your body is not a calculator - it’s a hormonal system designed to keep you alive. When you consistently eat below your energy needs (especially under 1500 calories/day), your body sees it as a famine and adapts by:

•  Slowing down your basal metabolic rate (you burn fewer calories at rest)
•  Suppressing thyroid hormone production, especially T3, the active form
•  Increasing Reverse T3, which blocks thyroid function and energy output
•  Reducing leptin, your satiety hormone, and increasing ghrelin, the hunger hormone
•  Triggering muscle loss, which further decreases your metabolic flexibility

All of this makes it harder to lose weight long-term - and much easier to regain it once you eat “normally” again.

What to do instead:
☑️ Focus on nutrient density over calorie restriction

☑️ Eat enough to fuel your thyroid, brain, and hormones - especially protein and healthy fats 

☑️Calculate your BMR(basic metabolic rate) and stay above it

☑️ Cycle in recovery days or higher-calorie days to keep your metabolism responsive

☑️Consider a reverse dieting phase if you’ve been in a deficit for a long time (slowly increasing intake to rebuild metabolic function)

Chronic undereating is not a willpower win - it’s a metabolic trap.

THE BIG PICTURE?

After 40, your metabolism is no longer just about calories in/calories out. It’s a delicate dance between thyroid health, hormone balance, nervous system support, and nourishment.

You can’t afford to ignore your levels of inflammation, your gut health, what your immune system is doing or how well your liver works.

It’s not about doing more, but doing what’s right for your current physiology.

When you do what’s right, you’ll see the results.

If finding your way through the labyrinth of your health feels overwhelming, and you’d love someone to do all the thinking, planning, and strategising for you — my team and I are here, with our clinical experience, sharp analytical minds and compassionate hearts, ready to support your every health and wellbeing need.

Book your discovery call here