Moodiness, Weight Fluctuations and Immune System Havoc – Why Shift Work Is To Blame.

Healthy Shift Worker items on an aqua background, including an alarm clock and foods to help with sleep inclugin kiwi, nuts, oats, salmon, chamomile

Do you ever have days when you’re feeling a little moody or irritable? Perhaps you’ve been struggling with ongoing weight fluctuations coupled with a depleted immune system?

If you work 24/7, chances are you’ve experienced at least one of these complaints.

So let’s talk about moodiness. Ongoing sleep deprivation certainly fosters feelings of bad-temperedness but have you ever really wondered why?

Well considering sleep is absolutely vital for our health, it’s not surprising that you feel this way.  Some of the many benefits of sleep include the following:

  • to enable our brains to conserve energy,
  • to assist in the repair and growth of tissues and muscles,
  • and to help restore cognitive function.

A restful slumber also helps the body to remove the build-up of adenosine, a sleep regulating substance which influences our sleep drive or our level of tiredness*.

So essentially when we sleep, excess adenosine is eliminated enabling us to feel more alert when we wake up, but because shift workers run on little sleep we’ve essentially got traces of adenosine still left in our system when that alarm clock goes off.

This contributes to feelings of drowsiness and you guessed it – moodiness and irritability!

But it’s not just an excess of adenosine that’s influencing our behaviour – so to do our hormones.

Hormones are chemicals which form part of our endocrine system which are secreted directly into the blood by an array of different glands including the pituitary, hypothalamus, thymus, pineal, testes, ovaries, thyroid, adrenal, parathyroid and pancreas. These glands are involved in growth, metabolism and our sympathetic nervous system or “fight or flight” response to stress.

When these glands are working normally, it enables our body to stay in a state of homeostasis or balance.

The trouble for shift workers is that a lot of these hormones are subject to diurnal variation i.e. influenced by the time of day.

For example, cortisol which is produced by the adrenal glands affects the metabolism of carbohydrates, proteins and fats which in turn affects our glucose levels. Cortisol also suppresses the immune system during times of stress which is not ideal when faced with a challenging day at work.  Normally our cortisol levels peak between 6-8am, and drop around midnight** however as this hormone is influenced by diurnal variation (particularly those working night shift), these hormones can become imbalanced.

So my big take home from this is don’t beat yourself if you’re experiencing moodiness, weight fluctuations and a depleted immune system.  

  • If you’re not getting enough sleep (which is always the case when working 24/7), and your body is unable to flush out the excess adenosine from your system, then you’re going to feel tired – and with tiredness comes a certain element of irritability.
  •  If your body is unable to convert the fuel in the food that you eat into energy as a result of a disrupted metabolism, then it can certainly have an influence on your weight.
  • And if your cortisol levels are being suppressed when you really need it during those stressful times at work, then it’s going to have an impact on your immune system.

So knowing how adenosine plays an important role in our sleep/wake regulation, along with our hormones being subject to diurnal variation – it can certainly be tricky to maintain that glamourous svelte figure, a robust immune system and cheerful demeanour when working 24/7!

*Reference – Why Do We Sleep Anyway?

**Mosby’s Manual of Diagnostic and Laboratory Tests


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