The Four Biggest Threats To Your Metabolism

Metabolic dysfunction and diseases that arise from it are now the dominant health challenge of our time. There is a reason that I talk about it so much and have built so much of my work around it. Just take a look at what is plaguing our healthcare service in this day and age. It extends far beyond obesity and type 2 diabetes, but fuels cardiovascular disease, neurodegeneration, cancer risk, and premature aging too. The prevalence of poor metabolic health continues to rise, even among those with a “normal” body weight. This begs a pretty big question: what exactly is breaking our metabolic machinery?

The mechanisms are complex and multifactorial, but four clear things consistently emerge — refined and ultra-processed foods, circadian misalignment, chronic psychological stress, and physical inactivity. Each of these doesn’t just nudge the system off course; they fundamentally rewire the metabolic landscape in ways that are often invisible until pathology emerges.

1. Ultra-Processed Foods: Modern Convenience, Metabolic Chaos

You will be no stranger to this message by now I am sure. There has been so much great work on increasing awareness of UPF's. In today’s world, more than half of the calories in the typical Western diet come from ultra-processed foods (Monteiro et al., 2018). These aren’t just convenience foods — they’re industrial creations: fizzy drinks, crisps, packaged snacks, sweetened cereals, ready meals, and products that have been reengineered to look, taste, and feel like real food, but are far from it.

What makes them so problematic - apart from their often hideous taste and texture? They’re loaded with refined carbohydrates, cheap industrial seed oils, salt, and artificial additives — and almost entirely stripped of fibre, protective nutrients, and plant-based compounds that normally support metabolic health.

Refined carbs in particular are a metabolic minefield. Because they lack fibre and structure, they’re broken down and absorbed rapidly, sending blood glucose soaring. The body responds by pumping out insulin to bring those levels down — but when this happens over and over, day after day, the system begins to break down. The result is chronically high insulin levels (hyperinsulinemia) and, eventually, insulin resistance — the cornerstone of metabolic disease (Ludwig, 2002). I know you have heard me say this on repeat but there really is a good reason for it. 

However, there’s more going on here than just blood sugar swings. Ultra-processed foods interfere with your brain’s ability to regulate appetite. They mess with the hormonal signals that tell you when you’ve had enough, and make it much easier to eat past fullness. Essentially, they hijack your reward system — activating dopamine pathways in a way that keeps you reaching for more (Hall et al., 2019). At the same time, this kind of eating fuels low-grade, chronic inflammation — which quietly sets the stage for insulin resistance, fatty liver, and cardiovascular issues (Cordain et al., 2005).

And then there’s the gut. Diets high in UPFs tend to wreak havoc on the microbiome — the community of microbes that live in your digestive tract and help regulate everything from blood sugar to fat metabolism to immune balance. When you’re eating this way, beneficial bacterial metabolites like short-chain fatty acids decline, and the gut barrier can become compromised — nudging your body further into metabolic imbalance (Zinöcker and Lindseth, 2018).

In short, ultra-processed foods aren’t just “empty calories.” They actively undermine the regulatory systems that keep metabolism functioning well — and they do it from multiple angles at once.

2. Circadian Misalignment: When Our Body Clock Loses Track of Time

Human beings are wired to operate in sync with the natural 24-hour cycle of light and dark. It’s not just about sleep — almost every organ in your body runs on an internal clock. These biological clocks aren’t just ticking in the brain; they’re also found in your liver, pancreas, muscles, and fat tissue. Together, they help time key metabolic processes like how well your body responds to insulin, how efficiently you process glucose, and even how your cells produce energy (Panda, 2016).

When our daily routines — especially eating patterns — fall out of step with these internal rhythms, things start to unravel. Late-night snacking, skipping meals, or working irregular hours (like night shifts) all disrupt this carefully timed system. And the body doesn’t take it lightly. Even if you eat the same amount of food, eating it at the “wrong” time can lead to poor blood sugar control and an exaggerated insulin response (Wefers et al., 2018).

This is because your body’s ability to handle carbohydrates changes throughout the day. Insulin sensitivity — the ability of your cells to respond effectively to insulin — is naturally highest in the morning and drops off as the day goes on. So, eating a big dinner at 9pm doesn’t just “sit heavier” — it literally causes higher blood sugar and insulin levels than if you'd eaten the same meal earlier in the day (Morris et al., 2015).

When your circadian rhythm is disrupted over time, it affects your metabolism on a deeper level too. It alters the way your genes regulate fat metabolism, energy production, and cellular clean-up processes like autophagy. At the same time, it can raise stress hormones like cortisol, increase inflammatory signals, and suppress melatonin — the hormone that helps regulate sleep (Reinke and Asher, 2019).

The problem? In our modern world of screens, irregular schedules, late-night meals, and chronic sleep disruption, being “out of sync” has become the norm — and it’s quietly sabotaging our metabolic health.

Aso someone who in recent years has started REALLY struggling with decent sleep, I can see first hand how much it has changed my own metabolism. It is my current dragon to fight and things are improving. If you have sporadic sleep it is really worthwhile trying to get on top of it to safeguard long term health. I will keep you updated on my journey!  

3. Chronic Psychological Stress: When the Alarm Never Switches Off

Stress isn’t what it used to be. Our ancestors needed it for survival — a quick burst of adrenaline and cortisol to escape a predator or respond to a threat. But in today’s world (isn't that the truth!), stress has become a background hum, always on, always simmering. Whether it’s money worries, deadline pressure, relationship strain, or relentless digital noise, the body interprets all of it as danger. And it responds accordingly — by activating the hypothalamic-pituitary-adrenal (HPA) axis and pumping out cortisol, our primary stress hormone (Sapolsky, 2004).

Now, cortisol isn’t the enemy. In short bursts, it’s useful. But when stress becomes chronic, and cortisol stays elevated, it begins to interfere with key metabolic processes. It tells the liver to keep producing glucose (even when it’s not needed), reduces insulin sensitivity in muscle and fat cells, and encourages fat storage — especially around the abdomen, where it’s most metabolically damaging (Rosmond and Björntorp, 2000).

Cortisol also changes how we eat. It makes us crave comfort food — the sweet, fatty, salty kind that lights up the reward centres in our brain. This creates a dangerous feedback loop: stress drives poor food choices, and poor food choices worsen our metabolic state.

It doesn’t stop there. Long-term stress can suppress testosterone and growth hormone, both of which play roles in muscle maintenance and blood sugar control. And let’s not forget the impact on sleep. Stress-related insomnia impairs glucose regulation, raises the hunger hormone ghrelin, lowers the satiety hormone leptin, and messes with how we process reward and impulse — making it even harder to resist that late-night snack (Spiegel et al., 1999).

What’s striking is that even if you’re eating reasonably well and staying active, chronic stress alone can tip you into insulin resistance, raise your blood lipids, and turn on inflammatory pathways (Black, 2006). It’s not just in your head — stress is deeply metabolic.

4. Sedentary Behaviour and Muscle Disuse: The Hidden Consequences of Sitting Still

We all know that exercise is good for us — but what we often overlook is the sheer amount of time we don’t move. Most adults now spend the majority of their waking hours sitting: at desks, in cars, on the sofa, staring at screens. And here’s the kicker — sedentary behaviour isn’t just the absence of exercise. It’s a distinct metabolic state with its own consequences (Hamilton et al., 2007).

When you’re not regularly engaging your muscles — through walking, lifting, stretching, even standing — your body starts to downregulate key processes. One of the most important is glucose uptake. Skeletal muscle is your biggest sink for blood sugar after meals, and inactivity causes those muscle cells to become less responsive. The number of glucose transporters (like GLUT-4) drops, and your mitochondria — the energy-producing powerhouses — start to lose their edge (Booth et al., 2012).

Meanwhile, prolonged sitting suppresses the activity of enzymes like lipoprotein lipase (LPL), which normally help clear fats from the bloodstream. When LPL is low, blood triglycerides climb, fat accumulates in the liver and other organs, and atherosclerosis can take root — all independent of how much you’re eating (Bey and Hamilton, 2003).

And it doesn’t take long for these effects to show. One study found that just five days of bed rest in healthy young adults led to a dramatic 67% drop in insulin sensitivity (Dirks et al., 2016). That’s how quickly your metabolic system can start to shut down when your muscles aren’t being used.

Muscle disuse also reduces AMPK activity — the cellular “fuel gauge” that keeps metabolism humming — and turns down the genes involved in fat burning and mitochondrial repair. It’s like turning the volume down on all the systems that keep you metabolically flexible and resilient.

In a culture built around convenience, this kind of stillness has become normal — and yet it quietly undermines the very systems we rely on to stay healthy.

Conclusion

Metabolic health doesn’t just unravel because of one bad habit or one dietary indulgence. It breaks down when multiple aspects of modern life converge — when we eat foods our biology isn’t equipped to handle, at times that clash with our internal clock, under stress that never ends, while barely moving our bodies.

Each of these factors — ultra-processed food, circadian disruption, chronic stress, and physical inactivity — chips away at our metabolic resilience. But together, they create a perfect storm. They don’t just add up; they amplify one another.

And yet, there’s power in understanding. Knowing how deeply these forces affect us isn’t meant to create fear — it’s meant to create awareness. Because once you see what’s really going on beneath the surface, you can’t unsee it. And that’s where meaningful change begins.

References

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Black, P.H. (2006). The inflammatory consequences of psychologic stress: Relationship to insulin resistance, obesity, atherosclerosis and diabetes mellitus, type II. Medical Hypotheses, 67(4), pp.879–891.

Booth, F.W., Roberts, C.K. and Laye, M.J. (2012). Lack of exercise is a major cause of chronic diseases. Comprehensive Physiology, 2(2), pp.1143–1211.

Cordain, L., Eaton, S.B., Sebastian, A., Mann, N., Lindeberg, S., Watkins, B.A., O’Keefe, J.H. and Brand-Miller, J. (2005). Origins and evolution of the Western diet: health implications for the 21st century. The American Journal of Clinical Nutrition, 81(2), pp.341–354.

Dirks, M.L., Wall, B.T., van de Valk, B., Holloway, T.M., Holloway, G.P. and van Loon, L.J. (2016). One week of bed rest leads to substantial muscle atrophy and induces whole-body insulin resistance in the absence of skeletal muscle lipid accumulation. Diabetes, 65(10), pp.2862–2875.

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Zinöcker, M.K. and Lindseth, I.A. (2018). The Western diet–microbiome–host interaction and its role in metabolic disease. Nutrients, 10(3), p.365.