In my practice, one of the most common things I hear is: "I think my metabolism is broken." It usually comes from someone who has just turned 40, or started perimenopause, or tried a strict diet last year that seemed to backfire afterwards. It's a completely understandable worry — but in my experience, what people call a "broken metabolism" is very rarely the real problem. Understanding what metabolism actually does, and doesn't do, changes how you approach your health.
What Your Metabolism Actually Is (and Isn't)
Metabolism is simply the sum of every chemical process your body uses to convert food into energy. It powers your heartbeat, breathing, digestion, brain function, and constant cell repair — not just the calories you burn at the gym. Everyone has a metabolism running around the clock, whether they're asleep, at their desk, or out for a run.
Here's what most generic advice leaves out: your basal metabolic rate (BMR) — the energy your body needs simply to stay alive at rest — typically accounts for around two-thirds of the calories you burn each day. Digesting food itself makes up roughly a tenth, and physical activity, both deliberate exercise and everyday movement like walking, fidgeting, and standing, accounts for the rest. This matters because most of your daily calorie burn happens regardless of how hard you train, which is one reason weight loss that relies purely on gym sessions, without attention to overall eating patterns, so often stalls.
The "Starvation Mode" Myth
I still hear clients worry that eating too little will "switch off" their metabolism and make them gain weight. This isn't how it works. Your body doesn't hold onto fat because you've under-eaten for a few days; if anything, prolonged severe restriction leads to continued weight loss, not weight gain.
What is real, and worth taking seriously, is metabolic adaptation. When you diet for a long period, particularly an aggressive one, your body does become somewhat more efficient and may burn slightly fewer calories than your body weight alone would predict. For moderate, sensible weight loss this effect tends to be modest, and it generally resolves once you return to eating at a stable, adequate level. The bigger risk with crash diets isn't a broken metabolism — it's losing muscle mass alongside fat, which genuinely does lower your calorie needs over time. This is exactly why I encourage clients to aim for gradual, sustainable change rather than severe restriction, particularly when gut health symptoms are also part of the picture, since under-eating can make digestive issues worse rather than better.
Life Stages and Conditions That Genuinely Change Your Metabolic Rate
Some life stages do bring real metabolic change, and menopause is the one I'm asked about most. Falling oestrogen levels during perimenopause and menopause are linked with a natural loss of muscle mass and a shift in where the body stores fat, both of which can lower your metabolic rate and make weight management feel different to how it did in your thirties. This isn't a personal failing, and it certainly isn't fixed by eating even less. I work with clients on menopause nutrition to adjust protein intake, strength work, and overall eating patterns for this new stage, though if you're experiencing symptoms that concern you medically, it's always worth discussing these with your GP alongside any nutrition support.
PCOS is another condition where metabolism and hormones are closely linked. Insulin resistance is common in PCOS, and because insulin plays a central role in how your body stores and uses energy, it can make weight management genuinely harder, not simply a matter of willpower. I support clients with PCOS nutrition around blood sugar-friendly eating patterns, though for diagnosis or medication questions, your GP or a specialist remains the right first point of contact.
The same is true of thyroid conditions such as hypothyroidism, and of diabetes, where blood sugar regulation and metabolic rate are closely connected. If you have a diagnosed thyroid or blood sugar condition, I'd always recommend discussing significant dietary changes with your GP or a registered dietitian, as these conditions sometimes need clinical management alongside general nutrition support. Where appropriate, I work alongside that care to help with everyday diabetes nutrition choices.
What About Weight-Loss Medications?
I'm increasingly asked about GLP-1 medications and metabolism, given how common these prescriptions have become. These medications work primarily by reducing appetite rather than directly changing your metabolic rate, but the rapid weight loss they can produce carries a real risk of muscle loss if protein intake and movement aren't prioritised alongside them, and losing muscle does lower your metabolic rate over time. This is one of the areas I focus on most closely with clients navigating GLP-1 support, making sure the weight lost is fat, not the muscle your metabolism depends on, while keeping your GP or prescriber informed of any significant changes to your eating pattern alongside the medication.
Practical Ways to Support Your Metabolism
None of this means metabolism is entirely out of your hands. While you can't dramatically overhaul your metabolic rate overnight, there is genuine, evidence-based scope to support it well:
- Include a source of protein at each meal — it has a higher thermic effect than carbohydrate or fat, and helps preserve muscle mass.
- Prioritise strength or resistance training two to three times a week, since muscle tissue burns more energy at rest than fat tissue.
- Stay active throughout the day, not just during workouts — everyday movement adds up to a meaningful share of your daily energy burn.
- Aim for consistent, good-quality sleep; poor sleep is linked with disrupted appetite hormones and reduced energy expenditure.
- Avoid very low-calorie or highly restrictive diets for extended periods, which risk muscle loss rather than genuine metabolic benefit.
- Stay well hydrated, as even mild dehydration can affect how efficiently your body functions.
If you would like personalised support with your metabolism, I offer one-to-one online consultations. View my consultation packages or book a free discovery call to discuss how I can help.