7 signs you need to get more sleep (that don't include yawning).

Image: iStock.

Some symptoms of lacking sleep — frequent yawning, struggling to remain conscious during all the exciting bits in Game of Thrones, earnestly researching whether coffee IV drips actually exist — aren’t particularly hard to decode.

But the tentacles of fatigue spread far and wide, and often its physical or mental presentations come right out of left field. Here are seven perhaps unexpected signs you need more one-on-one time with your pillow.

1. You suddenly have the appetite of a teenager

Fatigue can mess with your appetite and research suggests our hunger-controlling hormones aren’t immune to this.

According to Accredited Practising Dietitian and Accredited Nutritionist Sanchia Parker, increased levels of ghrelin and lower levels of leptin have been detected in sleep-deprived people. They sound like characters from Lord of the Rings, but they’re actually the hormones responsible for appetite stimulation and the reduction of hunger signals, respectively.

“The changes in hormone levels has the effect of making us feel more hungry, and less satisfied when we do eat,” Parker explains. Great.

2. Your cravings are out of control

Desperately craving a slice of cheesecake, two handfuls of sour worms... and half a loaf of Wonder White? When our bodies are crying out for sleep, they often begin craving foods that will deliver a quick, much-needed energy hit.

"Our bodies are smart and know that a chocolate bar or Coke will give us a quicker rush of energy than slow-burning brown bread or fruit," Parker explains. Unfortunately, there's a cruel downside to this logic.

"Because these foods are broken down in our body quickly, the hit of energy rapidly leads to an energy slump, making us more tired and in need of another hit of energy. Thus, a vicious cycle begins," she adds. Ugh. (Post continues after gallery.)

3. Your weight's changed

Parker says a lack of good quality sleep has been linked to weight gain and even obesity. One potential reason for this is that if you're not getting enough sleep, you have more opportunity to eat, and research indicates you're more likely to eat more when you're awake for more hours.

The junk food cravings mentioned above could also play into this. A 2013 study found when people were deprived of sleep for even one night, their brains responded to high-calorie food in a different way — notably, a reduction in frontal cortex activity, where our brains make rational decisions and consider consequence.

It's not just about food, either. "If you feel tired, the sofa and re-runs on TV starts to look more appealing than a run. Exercise can fall by the wayside when we lack sleep, which can be a factor in weight gain," Parker adds.

4. Sex? Oh God, no

Surprise! It seems sleep and your sex drive are closely linked.

A study of 171 women earlier this year found that for every additional hour of sleep subjects had, their likelihood of engaging in sexual activity with a partner was increased by a not insignificant 14 per cent. It's a similar story for men, with research indicating a link between poor sleep patterns and lower testosterone levels, which can diminish sex drive.

5. You're more emotionally vulnerable

If you notice a change in your mood and emotional reactions, you might want to examine your bedtime habits. Stephanie Allen, Principal Clinical Psychologist at Life and Mind Psychology, says insufficient sleep depletes our mental and emotional resources, making us less able to cope with everyday stress.

"If we don't get a good night's sleep, the next day we're more likely to feel anxious, even if we're not generally feeling anxious or stressed," she explains.

"It could be having a shorter fuse; things we might generally not pay much attention might be more likely to annoy us when we're sleep-deprived.We might be more likely to feel angry or upset. I think it means we're not as robust." (Post continues after video.)

6. You just can't concentrate, damn it

Similarly, fatigue can turn even the most switched-on among us into complete space cadets.

A lack of sleep has the power to impair our mental sharpness and cognitive abilities, including judgement, concentration, decision-making and memory. This certainly explains why you struggle to get through the working day after the office Christmas party.

"What we know in the research is that in terms of our ability to function cognitively... you need about five and a half to six hours of sleep a night as an adult," Allen says.

7. You're on Struggle Street at the gym

Aching muscles. Physical weakness. Sloth-like reflexes. Hand-eye-coordination to rival a toddler. Yep, a lack of sleep can seriously sabotage your performance during workouts — if you can even muster the motivation to pull on your runners.

How many of these have you experienced?