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You’re exhausted. So tired you don’t know how you’re going to get through the rest of the day. You need that energy hit and reach for the foods you know will give it to you – carbs, chocolate and a sugary caffeinated drink.

Sound familiar?

Whether it’s external factors (maybe a snoring partner or crying baby) or life’s stresses that keep you tossing and turning all night, when you’ve not caught many zzzs, it’s easy to reach for foods you ordinarily avoid.

What happens if this is a frequent occurrence? Will you inevitably always opt for the wrong food and be more likely to gain weight? If you try to lose extra pounds, will you find it harder because your tiredness saps your motivation? And does a good night’s sleep mean you’ll – more often than not – opt for food packed with nutrients that could aid weight loss? Most importantly, if you’re struggling with sleep and sticking to a diet, what can you do to improve both?

We looked into the science and received some advice for sufferers too…

Back in 2011, the – and subsequent media coverage – showing a link between poor sleep and weight. The investigated the relationship between sleep, stress and people’s attempts at weight loss. It also drew upon previous research showing a link between poor sleep and obesity. The NHS’ conclusion? While there were potential issues with the study, the results made sense: “It seems intuitive that if someone is not sleeping well and is under stress, then sticking to a weight-loss programme will be more difficult,” they said.

As the years have rolled on, further research has emerged, and it seems to show similar results.

“If you’re sleep-deprived, we know you’re potentially more emotionally fragile, so you’re more likely to make impulsive food choices”, says clinical diabetologist Professor Eleanor Scott of the University of Leeds. “A typical situation would be when people have small children who are awake in the night – they’re going to crave carbohydrate-rich foods the next day. They give us an instant energy boost when we’re feeling tired and make us feel good. We know sugar makes us feel better, but it’s only a temporary fix. So, sleep deprivation alters our emotional choices”.

This lack of motivation to eat ‘healthy’ food is very much biological, says Scott. “We know if you don’t get enough sleep it alters your hunger. There have been studies where people rate how hungry they feel, and when you ask people who’ve had a disturbed night’s sleep, their hunger increases and their ability to feel full after eating actually decreases. And we know some of the main hormones that are involved in controlling hunger are impacted. Leptin normally tells us when we’re full, but reduced sleep tends to cause lower levels of leptin, which is why people will still feel hungry.”

If we make poor food choices when we’re tired, does it follow that repeatedly not getting enough sleep could lead to issues with weight gain and obesity?

“There are enough big signals about what pre-empts weight gain and Type 2 diabetes that we can say if you’re not getting enough sleep on a regular basis, it strongly looks likely it will cause a problem,” says Professor Scott.

Research that backs this up has been produced by Dr Erin Hanlon, Research Assistant Professor at the University of Chicago, and her colleagues. In 2016, they wanted to see if sleep deprivation impacts chemical signals which, in turn, make people crave high-carbohydrate and high-fat foods.

With often focussing on how poor sleep impacts levels of the hormones ghrelin (which stimulates appetite) and leptin (which tells you you’re full), the scientists wanted to measure another chemical signal: endocannabinoid (eCB) – which is associated with making us crave ‘highly-palatable’ foods.

found that when sleep deprived, the participants’ eCB levels were increased and amplified. The result? The participants started reaching for unhealthy snacks because they didn’t feel full.

Looking back at the study and other research carried out, Dr Hanlon says “I personally feel confident there is a link between sleep deficiency and increased feeding, and moreover that sleep deficiency is one of the contributing factors in the rise in obesity”.

This view is backed up by other experts. “In large population studies, insufficient sleep (be it poor sleep quality or short sleep duration) is related to significantly worse long-term health outcomes, including higher incidence and prevalence of diabetes, increased prevalence of obesity and cardiovascular disease, and poorer mental health outcomes”, explains Dr Iuliana Hartescu, a member of Loughborough University’s Clinical Sleep Research Unit.

Dr Hartescu has studied the relationship between , which she describes as a ‘health trinity’. Her advice for those wanting to improve their diet and fitness levels? Before you start that health kick, make sure you’ve got your sleep routine under control. “When you’re more rested, you’re more likely to be physically active, more likely to eat at the right times of the day, and more likely not to let fatigue interfere with your motivation to stick to your diet.”

Having spent years studying the relationship between exercise, weight management and health, UCLA’s Dr. Christopher B. Cooper, together with a team at the university (with input from a chain of gyms), carried out research that focused on .

Over 12 weeks, two groups followed the same exercise and nutrition programme, but one also received a behavioural modification programme – a major part of which was sleep training. By the end of the study, the group without the additional training had lost on average 1.3 kilograms of fat mass. The group who received the additional training had lost 2.3 kilograms.

Dr. Cooper explains: “We were unable to demonstrate that we’d improved sleep quality, but intriguingly we improved exercise performance, aerobic quality – including oxygen uptake – and body composition. We saw significant reductions in the percentage of body fat at the end of the exercise training programme that had incorporated sleep training.”

However, says Dr. Cooper, there is still a lot of work to be done in the field. “Common sense shows us there has to be a relationship between sleep, weight management, exercise and other aspects of behaviour. Lots of studies clearly demonstrate associations, but it’s a much greater challenge to prove cause and effect. More studies are definitely required.”

“We are often keen to have a magic answer, but I would encourage stepping back and valuing and being kind to yourself,” says British Dietetic Association spokesperson and dietitian, Aisling Pigott. That’s not to say she doesn’t have tips that can help you during times of tiredness.

“Try to regulate your meal pattern, as this supports energy levels and your ability to make healthy choices. Choose simple, easy-to-prepare meals with fruit or vegetables. Stay away from ‘faddy’ or overly restrictive diets that can lead to over-eating, and sit down, relax and enjoy your meals with no computer, phone or laptop,” she says.

And if you’re after healthy, energy-boosting food, go for low-GI foods such as wholemeal carbohydrates, nuts and seeds and fruit and vegetables “which will allow a slow release of energy without making you feel sluggish,” says Pigott.

If you think you have insomnia...

Dr Dimitri Gavriloff, a clinical psychologist who specialises in sleep medicine for app Sleepio, explains that insomnia is classified as “struggling to fall asleep or stay a sleep at night, for longer than three days a week and for more than three months, and impacting on your ability to manage during the day.”

If you fall into this category, the first-line treatment recommendation is CBTI – Cognitive Behavioural Therapy for Insomnia.The therapy focusses on different behavioural treatments, one of which is stimulus control therapy, which aims to “re-establish a healthy association between being in bed and being asleep”.

“For people with insomnia, the bed often becomes associated with feelings of restlessness and being awake, so this is a means of trying to re-establish a good bed-sleep association.”

This treatment comes with five instructions, covering everything from not taking your work to bed, to following a ‘quarter-of-an-hour rule’, where you avoid staying in bed if you’re not asleep and only go back to bed when your sleepiness has returned.

As part of CBTI, a therapist may also advise ‘sleep restriction therapy’, where you reduce the amount of time spent in bed to the hours you are sleeping and then slowly increase it again. And cognitive therapy, “which is more about challenging unhelpful thoughts and psychological patterns people have.”

So what should you do if you think you’re suffering with insomnia and require help? “If you have a serious concern about your sleep, going to the GP is a really good way to start”, finishes Dr Gavriloff.