The Importance of Sleep for Weight Loss
The importance of sleep in regulating health and metabolism is becoming more widely recognised.
A study found that when subjects were deprived of sleep, at 4 hours a night, for four days; they took 40% longer than normal to regulate blood sugar levels after a high carbohydrate meal. 1.]
Another study showed that when slow wave sleep was suppressed for three nights; the subjects became 25% less sensitive to insulin. 2.]
The hypothalamus in the brain controls the appetite and fat burning, as well as insulin sensitivity and glucose control.
If insulin and glucose control are adversely affected, this is a sign that the hypothalamus is not working as well.
If the hypothalamus is not working as well, appetite and fat burning will be similarly negatively affected.
Another study, supporting this, found that when subjects were deprived of sleep for 2 nights (4 hours per night) , leptin (the satiety hormone) levels decreased by 18% and ghrelin (the appetite hormone) levels increased by 28%.
There was a 23% increase in reported hunger level and subjects also preferred high carbohydrate foods (sweets, salty food and starchy food). Craving for salty food increased by 45%. 3.]
An abundance of studies make it very clear that quality and quantity of sleep is very important for resetting the brains metabolic regulating centre.
How Does Sleep Affect Metabolic Health, Appetite and Body Weight?
Melatonin is a hormone which is released at night.
It controls the sleep/wake cycle.
Melatonin also plays an important role in controlling the brains master metabolic regulator - the hypothalamus.
Daily melatonin administration to middle-aged rats to restore youthful plasma melatonin levels also decreased body weight, belly fat, leptin and insulin levels to more youthful levels. 4.]
Melatonin, released at night, whilst you sleep; not only ensures a good night sleep, it also powers up the hypothalamus, which results in a cascade of positive health effects, including reduced appetite.
It is therefore crucial to take measures that will increase melatonin levels at night.
However, melatonin released in the day has the opposite effect.
Melatonin released in the day, will make you feel tired, sluggish and hungry.
In the day, the hormone which has the positive effects to power up the hypothalamus is dopamine.
Too much dopamine at night will stop you sleeping well. E.g. when you have too much caffeine at night.
The ideal scenario is high dopamine in the day to keep you feeling alert and to keep appetite low.
And then high melatonin at night, to ensure a deep sleep and a boost to the hypothalamus which will keep the appetite low in the following day.
Melatonin and dopamine regulate each other, so that when dopamine is high, melatonin is low and vice versa.
How do we ensure that dopamine is kept high in the day time and melatonin is kept high at night?
The answer is LIGHT.
Light switches off melatonin in the day and switches on dopamine.
When it gets dark in the evening, melatonin is switched on and dopamine is switched off.
This melatonin/dopamine response to light, ensures that we sleep well at night, but it also means that melatonin is confined to the sleeping hours and dopamine is confined to the waking hours, where they are best able to positively affect the function of the hypothalamus.
Natural light most powerfully switches off melatonin release in the day and switches on dopamine.
By getting an early morning dose of natural light, dopamine is switched on in the day and melatonin switched off.
This is the most desirable hormonal environment for getting the hypothalamus firing on all cylinders to make you feel full of energy, in a better mood, appetite under control, fat burning maximised and all aspects of health improved.
When we sleep, we instead want high levels of melatonin and low levels of dopamine.
This not only ensures a good night of sleep, but ensures that melatonin is increased optimally whilst we sleep and this is when melatonin has its power to rejuvenate the hypothalamus.
At least half an hour of natural light every morning is required to optimally switch on dopamine in the day.
When it gets darker in the evening, the absence of light causes melatonin production to increase dramatically about 2 hours later.
This is why it is important to keep lights dim in the evening before bed and avoid using the computer or phones (which emit strong blue light) at least an hour before bed.
If we keep levels of light low before bed time; when we go to bed, we will have built up high levels of melatonin, which will mean that we will be ready to fall asleep and melatonin release while we sleep will be maximised, which is the very time that melatonin has its power to rejuvenate the hypothalamus.
By getting the full 8 hours of sleep, we extend the release of melatonin, meaning that the hypothalamus gets the maximum dose of this powerfully corrective hormone.
It is therefore important to start getting ready for bed earlier to ensure a good 8 hours of sleep.
The darker it is at night, the more melatonin is released, so it is important that the bedroom is kept as dark as possible.
This means turning the landing light off, having curtains with a black-out effect and removing any devices which may emit light throughout the night.
Improving sleep habits is an easy strategy to put in place.
It is easier than dieting or exercise, yet just as powerful.
To neglect this strategy is to undo much of the good work and effort you put in to diet and exercise and should be prioritized!