We’ve all had days where you can’t stop yourself from thinking about sugary snacks. You feel compelled to nip to the shops, buy a bar of chocolate or a packet of biscuits, and eat them in one sitting. In your car.
There is actually a reason behind these seemingly uncontrollable urges and sugar cravings. There’s a science explaining why, sometimes, we can’t help but eat to excess, and also why some people are affected more than others.
The science of hunger
In order to survive, we must eat. It’s a very primal reaction in our bodies. When we are low on energy, the brain senses this dip in fuel – typically glucose – and fires off signals to other parts of the brain to make us desire food. Glucose is super important for brain functionality.
As such, the brain has multiple detectors that closely monitor the levels of glucose within blood vessels. These gauge whether there is enough glucose – and in turn, whether we should be hungry or satiated. If the levels are too low for the brain to work properly, we become more hungry. Seems simple enough.
The hypothalamus is an area of the brain that controls basal functions, such as temperature, hormone releases, and appetite. It produces the actual feelings of hunger we experience when we have low energy. However the part most involved in food intake and metabolism is the lateral hypothalamus.
To be brief, the lateral hypothalamus helps to release hormones, interacting with our digestive organs to make us feel hungry – your stomach starts to rumble, for example.
The most notable hormones in this whole process are orexin and neuropeptide Y. Both are quite powerful appetite hormones. In short, the more produced by the body, the more we desire food.
Giving in to those sugar cravings
So our hunger comes from the brain. How do we know when we’re full? This is communicated typically through hormones produced elsewhere in the body. The big players here are the well-known insulin and not so famous leptin.
Leptin is produced by fat cells, and the amount secreted is based on our own body fat level. So, if we have more fat, our appetites are reduced in line with this. This helps maintain homeostasis. Insulin however is produced by the pancreas when glucose is sensed.
But both hormones are secreted after eating to suppress hunger and satiate our appetites, and function in the brain’s “pleasure centres”. They bind to receptors in the brain to stop hunger signals from being sent to other parts of the body.
Still with me? Let’s talk about dopamine! You’ve probably heard about it before. It’s a feel-good hormone released in the brain’s pleasure centres. It’s produced when we want something, and when we actually get the thing we want. So insulin and leptin reduce our want for food, and also the pleasure we get from finally having it.
In food terms – if you really crave a bar of chocolate, a rush of dopamine is released. When you actually manage to get the chocolate, more dopamine is secreted. This is an evolutionary trait. When humans were hunter gatherers, food was scarce. Food high in sugar and fat was incredibly rare, and so when found it was logical to eat as much as possible.
Now that such delicious treats are readily available, we’re in a pickle.
Typically, leptin and insulin weaken the effects of dopamine. This means we feel full when we eat, as they reduce our want for food, and how much we enjoy what we are eating at that time.
Delicious, yet bad-for-you foods manipulate this system. They actually stimulate the release of hunger inducing hormones, and diminish indicators for feeling full and satisfied. This actually means we eat far more than we need.
Why does this happen? We still have these biological desires to eat high energy foods due to our evolutionary past. As such, our brains are wired to want these types of food, and to eat as much as possible when we find them.
When we eat the chocolate, more hunger hormones are released and since we enjoy it so, the pleasure centres in the brain kick into overdrive and intensify our desire for it. The brain tells itself it wants the food, more so than simply liking it. This magnifies cravings, making it really hard not to then make that trip to the shops to buy something tasty.
The impact of those satiety hormones is weakened greatly, meaning the brain keeps wanting to eat. This is why sometimes we eat and eat, with little or no effect on our appetite.
It’s not the same for everyone
Humans are uniquely individual, and so everyone has different hormonal reactions when eating. Metabolism is still somewhat a mystery, however there is evidence to suggest that some people simply don’t have as effective an ability to feel full after meals.
It’s addictive. The brain treats such food in the same way it would gambling, smoking, or drugs. They are all dealt with in the pleasure centre. Of course some people are more susceptible than others, and this is related to differences and deficiencies in the dopamine signals. Due to this, it can be more difficult for some to make and keep healthy lifestyle habits.
The reasoning behind an insatiable appetite then is pure manipulation. Our normal bodily processes are hijacked by donuts and burgers, and consequently our brains desire more and more food. It’s not necessarily by choice, or greed, that some people eat excessively.
Perhaps in understanding the physiological processes behind our appetites, you can give yourself a break. And maybe have more chance of reaching for a salad when you’re feeling peckish.
Do you have more questions about sugar cravings? Head over to the Auro Facebook group. We’ve got a whole community there, including our industry experts, sharing tips and advice on their own fitness experiences, so you don’t have to feel like you’re alone in your health journey.