Shakespeare said: “sleep …. knits up the ravelled sleeve of care,” and he was right.  But, as well as aiding our mental and emotional state in this way, enough of the right kind of sleep can help us avoid obesity and reduce our risk of disease, but how can we access sleep’s positive powers?

Sleep plays a key role in managing your metabolism and, therefore, your ability to process food into energy.  It modulates hormones that regulate appetite, food intake, calorie burning, fat storage, and body weight.  Hence, a healthy sleep routine optimises your metabolism and prevents obesity and metabolic diseases.

In this blog, I will explain how sleep influences your metabolism and body weight and why not enough can put you at risk of obesity, heart disease and dementia.  I will issue the sleep prescription that optimises your metabolism so you can enjoy sufficient energy levels, ideal body weight and lower your disease risk.

Traditional weight management focuses on advising people to eat less and exercise more.  This may have some limited effect.  However, sleep is the strongest factor influencing your metabolism.  It directly affects the hormones that regulate your appetite and calorie consumption (ghrelin and leptin) and sets your body’s ability to process sugar and burn fat.

Ghrelin, the hunger hormone, is released from the stomach.  It stimulates your appetite and food intake.  Leptin is a hormone produced by fat (adipose) cells, sending messages to the appetite centre in the brain (hypothalamus), giving you a sense of fullness and telling you to stop eating because you have enough calories on board to meet your needs.

Poor sleep stimulates your stomach to produce more ghrelin.  Higher levels of ghrelin and lower levels of leptin make you consume excessive calories – a recipe for obesity and metabolic disease.  Restful sleep is necessary to regulate your appetite and avoid cravings and weight gain.

Sleep deprivation also changes your food preferences towards palatable, energy-dense, processed and fast foods high in sugar, fat, and salt – again, a recipe for obesity.

Because you make energy whilst asleep, poor sleep is associated with lower energy levels.  This results in lethargy and tiredness, which of course, make you less likely to exercise.  In this case, your body diverts excess energy to be stored as fat.

One study reported that one night of shortened sleep (4.5 hours) elevated ghrelin levels in healthy individuals enough to make them feel hungry the following day.  Lack of sufficient sleep also reduces leptin, the hormone that suppresses appetite and promotes a feeling of fullness.

Other studies demonstrated that adequate quality sleep elevates leptin, inhibits ghrelin release during sleep, and supports night-time fasting.

Not dealing with sugar

Sleep deprivation and poor-quality sleep affect the body’s ability to process glucose and use insulin effectively.  This results in insulin resistance, high blood sugar and insulin levels.  Lack of enough or high-quality sleep also raises the stress hormone (cortisol), negatively impacting insulin sensitivity and blood sugar levels.

High cortisol at night interrupts sleep in people with mental and physical stress; it is also a feature in people with poor blood sugar control and those who consume alcohol, caffeine, and tobacco.

People with blood sugar problem usually wakes up between 1 and 2 am, after which they struggle to go back to sleep.  It is primarily due to the consumption of sugar and processed carbs at dinner, causing a sugar spike followed by a crash in those early hours.  These patients would benefit from resistant carbs such as beans in the evening meal.  Beans are rich in fibre and are digested slowly for many hours, releasing a little sugar to top up the blood sugar at night.

In one study, 11 young men were allowed 4 hours of sleep per night for 5 or 6 nights.  A glucose tolerance test was conducted after a high-carbohydrate breakfast.  Glucose tolerance decreased by 40% in sleep-deprived individuals compared with the fully rested control group.

A body of research also confirmed that insufficient sleep increases your risk of diabetes due to the negative impact on glucose metabolism.

Slow fat burning

Studies demonstrated that poor sleep reduces the body’s ability to burn fat.  In one study, short sleep resulted in more fat stored than consumed.  Having longer sleeps at the weekend improved fat metabolism but did not restore it to pre-sleep deprivation levels.

A 2020 Spanish study found that poor sleep in middle-aged, sedentary individuals resulted in lower fat-burning rates.  Even eating the Mediterranean diet did not diminish the adverse effect.

Adenosine triphosphate (ATP) is the energy molecule.  Made up of adenosine to which, energy is stored as phosphate bonds.  ATP power body cells to run their vital activities.  As the body uses the energy in ATP, adenosine builds up, interfering with brain activity, causing drowsiness, and inducing sleep.  High adenosine means your body has run out of energy.  The body builds a new energy reserve during sleep, and you wake up when adenosine gets too low.

This means you must have good physical activity during the day to enjoy restful sleep at night.

The quality of sleep

It may well be that you get enough hours of sleep but do not enjoy a restful sleep.  Quality sleep means falling asleep within 30 minutes of lying in bed, sleeping the recommended hours for your age, feeling rested, restored, and energised in the morning, waking up no more than once during the night, and falling back asleep within 20 minutes.

Poor quality sleep is common, particularly if you feel tired, groggy, and unsettled in the morning, depend on caffeine to stay awake during the day, have difficulty focusing or memorising recent events, and display poor performance at work and home.

The reasons for poor sleep include poor sleep hygiene, an irregular sleep schedule, consuming too much caffeine and alcohol, suffering from stress, depression, or anxiety, or experiencing inflammation, toxicity or nutritional deficiency.

Your sleep cycles

During the night, you cycle through two types of sleep – non-REM and REM – in four stages.  We experience each of these four-stage cycles 4-6 times each night, with each cycle lasting up to 90 minutes.

Stage 1 non-REM represents falling asleep (dozing off) and lasts up to 5 minutes.  During stage 2 non-REM, your temperature drops, muscles relax, and your breathing and heart rate slow down.  This lasts between 10 and 25 minutes.  During stage 3 non-REM, your body relaxes further, the brain exhibits delta (slow) waves, and your body’s restorative activity (growth and repair) takes place.  You restore your physical and mental health and optimise key body processes such as metabolism and the immune system.

You should have adequate deep sleep (stage 3 non-REM), also known as slow wave sleep (SWS), to enjoy a high-quality, restful sleep every night.  The restorative process usually takes place early at night, between 10 pm and 2 am, emphasising the wisdom of the saying, “early to bed, early to rise makes you healthy, wealthy and wise.”

One study demonstrated that sleep suppression in healthy adults for three consecutive nights decreased the SWS restorative sleep by 25%, reaching levels usually seen in older adults and patients with obstructive sleep apnoea (OSA) and creating a pattern that impairs glucose metabolism and increases the risk of diabetes. 

Growth hormone (GH) causes growth in children and repair in adults.  It increases during sleep and diminishes with sleep deprivation.  70% of GH production occurs early at night with the first phase of SWS.  Another reason for an early bedtime.

You should take your evening meal at least 2 to 4 hours before bedtime.  This allows your body to focus on reaping the benefits of sleep.  Your body cannot run two activities (sleep and digestion) simultaneously.

What makes you sleep?

Exposure to light during the day causes the master clock in the brain (hypothalamus) to send signals that generate alertness to keep you awake and active.  At night, the clock messages the pineal gland in the brain to produce tons of melatonin to give you restful sleep.

What you may not know about melatonin is that it is the master antioxidant that washes out the oxidants that build up during the day.  This is good news for your metabolism since the powerful antioxidant effect of melatonin preserves your mitochondria (energy plants) that otherwise would be vulnerable to oxidants’ damage.

The circadian rhythm influences metabolism and body weight by regulating blood sugar and fat storage.

Winter blues, or Seasonal Affective Disorder, is an excellent example of disruption of the circadian rhythm.  The same is observed in demented people who sleep during the day and stay awake at night.  Interestingly, the circadian rhythm also influences DNA repair, which is crucial in cancer prevention.

Night shifts interrupt the circadian rhythm and metabolism, resulting in weight gain and obesity.  Night shift workers have a slow metabolism, burning fewer calories than when they sleep at night.  Many studies have reported a far higher risk of obesity among night shift nurses than day nurses.

Sleeping outside the circadian rhythm is associated with a poor ability to process sugar, raising insulin and cortisol and triggering inflammation causing insulin resistance.

The circadian rhythm is also disrupted in obstructive sleep apnoea (OSA), a prevalent sleep disorder characterised by repetitive episodes of upper airway obstruction during sleep, leading to intermittent low oxygen, high carbon dioxide levels and interrupted sleep.

Research has documented a strong association between OSA and glucose intolerance, insulin resistance, weight gain and diabetes.  58-86% of patients with type 2 diabetes have OSA.

Studies have also reported that the respiratory support of OSA patients – CPAP (a night mask) lowers insulin levels, fasting blood sugar and haemoglobin A1C (a marker of glucose control over the last 3 months.)  The beneficial effect of CPAP was similar to that of the diabetic pill Metformin.

Acid reflux at night is a problem in stressed and overweight people, particularly those who have their last meal less than 2 hours before bedtime, especially if the food is fatty or spicy.  These patients may benefit from raising the head of the bed.

The Vitality Clinic sleep prescription

Early to bed at 10 pm or soon after

Aim for 7-8 hours of uninterrupted, restful sleep

Resistant carbs in the evening meal will prevent sleep interruption

Leave all screens one hour before bedtime for good sleep hygiene

Your circadian rhythm – with daytime sun exposure – will also deliver more vitamin D

You see, my friends, how important sleep is to our health.  We all sleep, of course – but do we enjoy sleep of the right length and quality?  As always, please ask any questions in the Comment section below – and please subscribe to the newsletter so that you don’t miss further vital information.  Thank you!



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