We get hungrier. Chronic sleep deprivation leads to an increase in appetite (and weight gain), shown by several studies. Our bodies prompt us to consume more kilojoules (to try keep us awake and chugging along)
and our ability to recognise a full stomach is shut down.
We get depressed. Our cortisol levels rise, and so does or blood pressure. There's increasing evidence that poor sleep causes chronic low-grade inflammation, which is linked to many diseases. All these factors can also lead to insulin resistance and diabetes.
We risk gaining weight. Another study shows that consistent bed and wake times are linked to less body fat among young women.
Read More: How to Fix Your Metabolism to Achieve a Healthy Weight
It affects our looks. Our skin has its own rhythms. During the day, skin is occupied with protecting itself from UV rays, pollution and environmental aggressors. At night, it works to repair the damage incurred in daylight hours and to regenerate and replenish its reserves. These actions are vital as skin cells can then produce more collagen and elastin and they multiply to rebuild the outer protective horny layer. So, in a way, our skin never rests.
When we're young, it manages this continuous labour well, but with time, the signs of fatigue start showing. And if we're sleep deprived, it doesn't matter how young we are, these vital functions aren't happening, and our skin is ageing before its time.
An Estée Lauder-commissioned study found that skin recovery in sound sleepers was 30 percent higher than their restless counterparts, and good quality sleep positively affects skin appearance almost twice as much as a poor night's sleep.