Why sleep matters for your metabolism

I used to be an insomniac... nights were long and restless, days were foggy-headed and craving quick fixes just to get me through.

Back then I had no idea how much my sleep – or lack of it – was affecting my metabolism and overall health.

Decades of research tells us that how well (and how long) we sleep has a direct impact on blood sugar, energy balance, hormones and even food choices.

Poor sleep isn’t just tiring – it actively disrupts the systems that keep our metabolism steady, with big consequences.

This is especially relevant in midlife, when changes in hormones, metabolism and lifestyle can make poor sleep even more impactful on our health.

Sleep, hormones and metabolic health

Sleep influences our hormones.

When sleep is cut short or disrupted:

• Appetite is increased

  Leptin, the hormone that signals fullness, is reduced, and ghrelin, the hormone that signals hunger, is increased.

  
  

• Blood sugar control is impaired

  Our bodies are less sensitive to the hormone insulin, which an lead to what's called insulin resistance.

  
  

• Fat storage is increased

  Caused by insulin resistance (above), raised levels of the stress hormone cortisol, and reduced levels of growth hormone.

• Muscle mass can decrease

  Sleep induces release of growth hormone, which is needed for muscle growth and repair. Muscle is highly metabolic: the more muscle you have, the more calories you burn, even when you're not exercising)

Because of these effects, it becomes much harder to maintain a healthy metabolism and weight, and our risks of obesity and type 2 diabetes are increased.

Cravings and lack of sleep

In addition to affecting appetite (above), lack of sleep also changes the way we respond to food.

The 'food reward system' – which drives the pleasure and motivation we get from eating – becomes more active when we are tired.

This means high-calorie, sugary or fatty foods suddenly feel more appealing, even if you’re not physically hungry.

A 2025 review found that sleep-deprived people crave more energy-dense foods high in sugar and saturated fat, and feel less desire for fruit and vegetables.

Over time, these cravings compound the metabolic effects of poor sleep and make it harder to maintain healthy weight and blood sugar control.

Stress and sleep

Chronic stress is a major contributor to disrupted sleep and can amplify its effects on metabolism.

Stress hormones like cortisol interfere with normal circadian rhythms, appetite regulation, and energy balance, increasing the risk of insulin resistance, weight gain, and other metabolic issues.

Psychosocial stress can also interact with poor sleep habits, creating a cycle that’s hard to break and further compromising metabolic health.

Sleep and gut health

Sleep also influences our gut health.

Poor or disrupted sleep can alter the composition and diversity of gut bacteria and increase gut inflammation.

These changes can, in turn, affect energy balance, blood sugar control, and fat storage, linking the gut directly to metabolic health.

Alcohol and sleep

Even small amounts of alcohol can disrupt sleep, particularly REM sleep, despite the common belief that it helps you fall asleep.

Regular alcohol consumption in the evening can therefore undermine both sleep quality and metabolic health.

Sex differences in sleep and metabolism

Research shows that women may be more sensitive poor sleep than men.

Disrupted sleep can have a greater impact on hormone regulation, appetite and metabolic outcomes in women, which is particularly important in midlife because perimenopause can further amplify these effects.

This highlights the importance of personalised approaches to sleep and metabolic health.

Why this matters

Poor sleep is not just a nuisance – it is a key modifiable factor in metabolic health.

If you struggle with energy, cravings, weight management, or blood sugar regulation, looking at your sleep – as well as your diet and stress – is essential.

Improving sleep is not about perfection, it’s about understanding the mechanisms and making informed choices that support your metabolism and long-term health.

Ready to support your sleep and metabolic health?

If disrupted sleep, cravings, blood sugar swings or low energy are affecting your life, you’re not alone – and you don’t need to face it on your own.

I work with men and women in midlife to improve sleep, optimise metabolic function, balance hormones and support long-term health.

Get in touch if you’d like personalised guidance to help protect your brain, boost your energy and take control of your metabolic health.

Contact me

Disclaimer

The information and advice I provided here is of a general nature and should never replace individual health or medical advice provided by your doctor or other healthcare professional involved in your care.