Dr Nick Fuller
Leading Obesity Expert at the University of Sydney and founder of Interval Weight Loss.
Benjamin Franklin, one of the founding fathers of the United States, famously said nothing is certain except death and taxes. But I think we can include “you’ll feel hungry when you’re trying to lose weight” as another certainty.
The reason is basic biology. So how does this work – and what can you do about it?
Several hormones play an essential role in regulating our feelings of hunger and fullness. The most important are ghrelin – often called the hunger hormone – and leptin.
When we’re hungry, ghrelin is released by our stomach, lighting up a part of our brain called the hypothalamus to tell us to eat.
When it’s time to stop eating, hormones, including leptin, are released from different organs, such as our gut and fat tissue, to signal to the brain that we’re full.
But when we change our diet and start losing weight, we disrupt how these appetite hormones function.
This triggers a process that stems from our hunter-gatherer ancestors. Their bodies developed this mechanism as a survival response to adapt to periods of deprivation and protect against starvation.
The levels of hormones managing our hunger increase, making us feel hungrier to tell us to eat more, while the ones responsible for signalling we’re full decrease their levels, intensifying our feelings of hunger.
We end up increasing our calorie consumption so we eat more to regain the weight we lost.
But worse, even after the kilos creep back on, our appetite hormones don’t restore to their normal levels – they keep telling us to eat more so we put on a little extra fat. This is our body’s way of preparing for the next bout of starvation we will impose through dieting.
Fortunately, there are things we can do to manage our appetite, including:
One of the easiest ways to manage our feelings of hunger throughout the day is to eat most of our food earlier in the day and taper our meal sizes so dinner is the smallest meal.
Research shows a low-calorie or small breakfast leads to increased feelings of hunger, specifically appetite for sweets, across the course of the day.
Another study found the same effect. Participants went on a calorie-controlled diet for two months, where they ate 45% of their calories for breakfast, 35% at lunch and 20% at dinner for the first month, before switching to eat their largest meal in the evening and their smallest in the morning. Eating the largest meal at breakfast resulted in decreased hunger throughout the day.
Research also shows we burn the calories from a meal 2.5-times more efficiently in the morning than the evening. So emphasising breakfast over dinner is good not just for hunger control, but also weight management.
Protein helps contain feelings of hunger. This is because protein-rich foods such as lean meats, tofu and beans suppress the appetite-stimulating ghrelin and stimulate another hormone called peptide YY that makes you feel full.
And just as eating a breakfast is vital to managing our hunger, what we eat is important too, with research confirming a breakfast containing protein-rich foods, such as eggs, will leave us feeling fuller for longer.
But this doesn’t mean just eating foods with protein. Meals need to be balanced and include a source of protein, wholegrain carb and healthy fat to meet our dietary needs. For example, eggs on wholegrain toast with avocado.
Nuts often get a bad rap – thanks to the misconception they cause weight gain – but nuts can help us manage our hunger and weight. The filling fibre and good fats found in nuts take longer to digest, meaning our hunger is satisfied for longer.
Studies suggest you can include up to 68 grams per day of nuts without affecting your weight.
Avocados are also high in fibre and heart-healthy monounsaturated fats, making them another excellent food for managing feelings of fullness. This is backed by a study confirming participants who ate a breakfast incorporating avocado felt more satisfied and less hungry than participants who ate a meal containing the same calories but with lower fat and fibre content.
Similarly, eating foods that are high in soluble fibre – such as beans and vegetables – make us feel fuller. This type of fibre attracts water from our gut, forming a gel that slows digestion.
When we take time to really be aware of and enjoy the food we’re eating, we slow down and eat far less.
A review of 68 studies found eating mindfully helps us better recognise feelings of fullness. Mindful eating provides our brain enough time to recognise and adapt to the signals from our stomach telling us we’re full.
Slow down your food consumption by sitting at the dinner table and use smaller utensils to reduce the volume of food you eat with each mouthful.
Sleep deprivation disturbs our appetite hormones, increasing our feelings of hunger and triggering cravings. So aim to get at least seven hours of uninterrupted sleep a night.
Try switching off your devices two hours before bed to boost your body’s secretion of sleep-inducing hormones like melatonin.
Stress increases our body’s production of cortisol and triggers food cravings.
So take time out when you need it and set aside time for stress-relieving activities. This can be as simple as getting outdoors. A 2019 study found sitting or walking outdoors at least three times a week could reduce cortisol levels by 21%.
When we change our diet to lose weight or eat healthier, we typically restrict certain foods or food groups.
However, this heightens activity in our mesocorticolimbic circuit – the reward system part of the brain – often resulting in us craving the foods we’re trying to avoid. Foods that give us pleasure release feel-good chemicals called endorphins and learning chemicals called dopamine, which enable us to remember – and give in to – that feel-good response.
When we change our diet, activity in our hypothalamus – the clever part of the brain that regulates emotions and food intake – also reduces, decreasing our control and judgement. It often triggers a psychological response dubbed the “what-the-hell effect”, when we indulge in something we think we shouldn’t feel guilty about and then go back for even more.
Don’t completely cut out your favourite foods when you go on a diet or deprive yourself if you’re hungry. It will take the pleasure out of eating and eventually you’ll give into your cravings.
This article was originally published in The Conversation.
Dr Nick Fuller is the founder of Interval Weight Loss and is a leading obesity expert at the University of Sydney with a Ph.D. in Obesity Treatment. Dr Fuller is also the author of three best-selling books and his work been published in top ranked journals in the medical field, including JAMA, Lancet and American Journal of Clinical Nutrition.