Why Your Metabolism Isn’t Broken – It’s Responding
Weight that won't shift and energy that crashes usually aren't signs of a broken metabolism. A GP's guide to what's actually driving it, and what helps.
If you’re tired all the time, sleeping badly, and carrying weight that has shifted without any obvious change in what you’re doing – and you’ve put all of it down to a busy few months – you may be closer to the answer than you think.
But stress isn’t only a feeling.
One of the most common things we hear in clinic is some version of “I know I’m stressed, but I haven’t got time to deal with it.” It’s usually said with a degree of guilt, as though addressing it were a luxury to be earned once everything else is done.
Chronic stress is a metabolic disruptor. Managing it is medicine, not self-indulgence.
Most people understand stress as a response to a difficult period – a demanding job, a family situation, a general sense of too much and not enough time. It is all of those things. It is also a set of concrete physiological events with measurable consequences.
When the brain perceives a threat, real or anticipated, it triggers a hormonal cascade ending in the release of cortisol. In the short term this is useful: cortisol raises blood glucose, sharpens focus, and redirects resources to meet the immediate demand.
The problem is chronic activation – when the stress response is triggered repeatedly and never fully switches off.
Cortisol affects insulin sensitivity and influences where fat is stored, with a tendency towards the central, visceral pattern most associated with cardiovascular and metabolic risk.
This is why body composition can change while diet and activity haven’t, and why calorie arithmetic often fails to explain what someone is experiencing.
Cortisol should be high in the morning and low at night. Chronic stress distorts that rhythm, keeping cortisol elevated into the evening when it should be falling.
Poor sleep then dysregulates the stress response further. It is a self-reinforcing cycle, and by the time most people notice it, it no longer matters which came first.
The hippocampus is particularly sensitive to cortisol. Prolonged elevation is associated with difficulty concentrating, low mood and anxiety.
These have a physiological basis, not just a psychological one.
There is more that doesn’t announce itself. Chronic stress suppresses aspects of immune function while driving low-grade systemic inflammation, and sustained sympathetic activation raises heart rate and blood pressure independently of other risk factors. These effects accumulate over years, often invisibly, and they compound each other – which is why chronic stress is so often the underlying driver of conditions that appear unrelated to it.
Stress can’t be eliminated. Nobody negotiates their way out of a demanding job or a difficult year.
What can change is how completely the body recovers between demands, and how often it gets the chance to. The three below are here because they’re practical, not because they sound good.
Four counts in, four counts hold, four counts out, four counts hold. Repeat for two to four minutes.
This activates the parasympathetic nervous system via the vagus nerve – the counterpart to the stress response. It is one of the fastest ways to shift your physiological state. Use it before a difficult meeting, after a stressful commute, or when the evening wind-down isn’t happening.
Two minutes. Anywhere. No equipment.
Cortisol is naturally elevated in the first hour after waking. That is normal and helpful.
Checking your phone immediately layers information, decisions and social comparison on top of that peak, amplifying the stress response before the day has begun. A consistent boundary here has an effect out of proportion to how small it sounds.
Not a lighter day. A day with intentional unstructured time, where nothing needs to be optimised or achieved.
The body and brain require genuine downtime to consolidate, repair and regulate. Chronic busyness without recovery is a physiological stressor in its own right, regardless of how manageable it feels.
This is hyperarousal: being physiologically activated despite genuine fatigue.
In a well-regulated system, cortisol drops through the evening, allowing melatonin to rise and sleep to follow. When the stress response has been chronically stimulated, that evening drop doesn’t happen cleanly. Cortisol stays elevated and the brain remains alert even as the body is depleted.
The interventions that help most are the ones that actively signal safety to the nervous system: a consistent wind-down routine, a cooler room, limiting screens, and the breathing technique above. Most people need two to three weeks of consistency before they notice a real shift.
If it’s persistent and significantly affecting your sleep, it’s worth a proper consultation. There are sometimes hormonal or other factors worth investigating.
One pattern we’re seeing more of is high-functioning burnout.
Patients who are, by every external measure, coping well – careers, families, social lives – but whose physiology tells a different story. Elevated resting heart rate. Disrupted sleep. Weight that has shifted without obvious cause. A flatness they struggle to articulate.
The difficulty is that it doesn’t feel like burnout from the inside. It feels like a slightly harder version of normal.
If any of this sounds familiar, it’s worth paying attention to early. The sooner it’s addressed, the less it costs you.
If you’d like to explore any of this in the context of your own health, we offer consultations designed for exactly this kind of picture. You can book a free, no-pressure discovery call with either of us.
Dr Helen Kay and Dr Greta Gregory are GPs and lifestyle medicine physicians, and the co-founders of The Lifestyle GP.
This article is for general information and does not replace individual medical advice.
