Most of us have experienced it.
You have a terrible night's sleep and the next day you seem to be thinking about food constantly. The biscuits in the back of the cupboard are now on the radar and you find yourself reaching for a sweet snack in the afternoon and by the end of the day you may be looking for something comforting and easy.
It's very easy to think this is simply because you're tired. But there is actually a lot more going on.
In clinic, when someone comes to me saying, "I'm gaining weight and I don't understand why. I haven't changed what I'm eating," one of my first questions is "How are you sleeping?"
Sleep isn't just about how perky you feel the next day. It influences appetite, food intake, blood sugar regulation, non exercise activity thermogenesis, and the way our brains respond to food.
And that means that when you've had a poor night's sleep, the struggle to make healthy food choices and move your body is not as simple as willpower.
Why are you so hungry after a bad night's sleep?
When we're sleep deprived, our biology changes. Research has found that after sleep restriction, people feel hungrier and will eat more.
At the same time, the foods that are high in sugar and fat suddenly become more rewarding to the brain, making those quick-energy foods particularly difficult to resist.
Research tells us that after a disrupted or partial night’s sleep, on average a person will eat 385 calories more. Do that day after day and you’ll soon see a difference in how your clothes fit.
So if you wake up after a terrible night and feel like you're suddenly ravenous, you're not imagining it. Sleep loss can change the way your body regulates hunger and how your brain responds to food.
This is important because it means that the food choices you make after a poor night's sleep aren't always about willpower or knowing what you "should" eat. That goes out the window. Your physiology is influencing the signals you're receiving and the way you're responding to food.
Rather than responding to a bad night's sleep by trying to eat as little as possible, I prefer to think about how we can make nourishing food choices easier on those days. A proper meal with protein, fibre, healthy fats and complex carbohydrates (with all their fibre) can give your body what it needs while helping you feel more satisfied, before the biscuits start talking to you from the back of the cupboard.
Your brain starts looking for quick energy
Sleep doesn't just influence how hungry you feel. It can also change the way your brain responds to food.
When we're tired, foods high in sugar and fat can become particularly appealing because they activate the brain's reward pathways, involving dopamine. These foods provide a readily available source of energy and can be harder to resist when you're already feeling depleted.
Then there's the modern food environment. Advertising, supermarket displays, café cabinets, vending machines and social media constantly expose us to highly appealing foods. When you're well rested, you may be able to walk past those cues without giving them much thought. After a terrible night's sleep, they can become much harder to ignore. They now become signals to survival.
So reaching for that afternoon slice or chocolate bar isn't necessarily about suddenly having less discipline. You may be experiencing a combination of increased hunger and a stronger reward response to food.
What about ghrelin and leptin?
You may have heard of two hormones called ghrelin and leptin. Ghrelin is often described as a hunger hormone, while leptin helps signal satiety, or fullness.
Sleep restriction can influence these appetite regulating systems, although research findings are not entirely consistent. Some studies have found changes in ghrelin and leptin following restricted sleep, but the response can vary between individuals and studies. There is clearly more for us to learn.
What is more consistent is the bigger picture: poor sleep can increase hunger and food intake and make energy dense foods more appealing. We don't need to focus on one particular hormone to understand why your appetite may feel very different after a poor night's sleep.
Poor sleep can also affect your blood sugar
This is particularly important for people who are already struggling with blood sugar regulation, insulin resistance or weight.
Insulin is one of the hormones responsible for helping glucose move from your bloodstream into your cells, where it can be used for energy. When your cells become less sensitive to insulin, they don't respond as effectively, and your body may need to produce more insulin to achieve the same result.
Research has shown that sleep restriction can reduce insulin sensitivity, sometimes even after a relatively short period of disrupted sleep. One bad night doesn't suddenly make you insulin resistant, but repeated poor sleep may contribute to a less favourable metabolic environment.
If someone is struggling with blood sugar regulation, weight or persistent cravings, I don't just want to look only at what's on their plate. I also want to understand what's happening at night.
Why weight management is about more than calories
We all understand the basic idea of energy balance, but human physiology is much more complicated than simply deciding how many calories to eat.
Sleep, stress, hormones, appetite, insulin sensitivity, activity levels and the foods available to us all interact. This is why I don't like reducing weight management to simply "eat less and move more". Those things can be part of the picture, but they don't explain everything that influences someone's appetite, metabolism and ability to maintain a healthy weight.
I see this quite often with women who come into clinic because their weight has changed despite not consciously changing their diet. Hormonal changes, perimenopause, insulin resistance, medications, reduced muscle mass, changes in activity, stress and digestive health can all be relevant.
Sleep is one of the first things I want to understand. Are you getting enough hours? Are you waking during the night or struggling to get back to sleep? Are you lying awake worrying, or relying on caffeine to get through the day? If you're consistently sleep deprived, we can spend all day talking about food choices without addressing one of the biggest factors that may be influencing those choices in the first place.
Don't respond to poor sleep by restricting more
If you've had a terrible night's sleep and wake up feeling ravenous, my advice is don't punish yourself for it. Trying to eat as little as possible that day may leave you feeling even more hungry, tired and dissatisfied. That’s unsustainable. Eventually your survival strategies will kick in, and you’ll make choices that aren’t in your control.
Instead, focus on making your meals nourishing and satisfying. Include a good source of protein, plenty of fibre rich plant foods, healthy fats and a suitable source of carbohydrate. Drink plenty of water and aim for proper meals rather than trying to get through the day on coffee and willpower.
Protein is particularly useful here. It supports satiety and provides the building blocks your body needs to maintain muscle. I am always encouraging clients to include a good source of protein at breakfast, lunch and dinner, rather than leaving most of their intake until the evening.
Eggs, Greek yoghurt, chicken, fish, tofu, legumes and lean meat are all useful options. Combine these with colourful vegetables, wholegrains, kumara, fruit, nuts and seeds to create meals that provide sustained nourishment and help keep you satisfied.
Don't underestimate the importance of your evening meal
There is another side to this conversation. If you're trying to improve your sleep, what and when you eat in the evening can matter too.
Eating a very large meal late at night means your digestive system is still working through that food while your body is trying to transition into sleep. For some people, this can contribute to digestive discomfort or reflux, particularly if they lie down soon after eating.
If you need to eat late because of shift work or other commitments, a lighter meal may be more comfortable than having your largest meal immediately before bed. You don't need to eat dinner at exactly 6pm every night, but it is worth avoiding very late, very large meals as a regular pattern if they're interfering with your sleep or digestion.
Sleep needs to be part of your health plan
Whether your goal is to manage your weight, improve your gut health or simply feel better during the day, sleep deserves attention alongside nutrition and movement.
Start with the basics. Make your bedroom as dark as possible, keep your sleep and wake times reasonably consistent, get natural light during the day and be mindful of caffeine, particularly later in the afternoon. Give yourself some time to wind down before bed rather than moving straight from a busy day into trying to sleep.
It's also worth looking at the size and timing of your evening meal. You can read more about the foundations of better sleep in my article [Why You're Not Sleeping Well (and What You Can Do About It)].
Don't turn sleep into another thing to stress about
There is one final thing I want to mention. Sometimes when people learn how important sleep is, they start worrying about sleep.
"I have to sleep eight hours or I'll be hungry tomorrow."
"If I don't sleep tonight, I'll ruin my diet."
And suddenly sleep itself becomes another source of pressure.
That's not helpful. Sleep is important, but you don't need to have a perfect night every night. If you have a bad night, simply recognise that you may be hungrier the next day, you may crave more energy-dense foods and you may feel less motivated to cook.
That's okay. It doesn't mean you've failed.
It simply means you need to support your body a little differently that day. Have a proper breakfast, eat a nourishing lunch, keep easy, healthy food readily available and then work on getting yourself a better night's sleep the following night.
The takeaway
If you find yourself unusually hungry after a poor night's sleep, don't immediately assume that you've lost your willpower. Your biology may be driving your choices.
Sleep restriction can increase hunger and food intake, make high-energy foods more rewarding and reduce insulin sensitivity. That doesn't mean you need to be frightened of food or obsess about getting the perfect eight hours.
It means that if you're trying to improve your gut health, manage your weight, regulate your blood sugar or simply feel better in yourself, sleep deserves to be part of the conversation.
And if you've had a terrible night's sleep, don't punish yourself. Feed yourself well, make the next meal a nourishing one and then give your body the best chance you can to sleep well tonight.
Listen To The Podcast
If you'd like to hear Tracy talk about why sleep changes hunger, cravings and food choices, listen to Why (No) Sleep Makes You Hungry and What to Do About It on The Most FM.
If you want to hear more, check out these podcasts too:
