Why Do You Crave Junk Food?

You’re sitting at your desk, it's mid-afternoon, and you've had a productive day so far. Suddenly, out of nowhere, the urge hits you.

The perfect piece of chocolate bar is calling your name. You can almost taste the sweet, velvety chocolate melting in your mouth.

You try to ignore it, but the overwhelming desire for the chocolate only grows stronger and stronger.

This is the classic experience of a craving — the intense desire for a particular food or flavor.

Craving differs from hunger in the sense that hunger can be alleviated by any type of food whereas cravings are usually only satisfied after eating a certain type of food.

Cravings are subjective: some people desire sweet foods, while others yearn for salty or sour foods.

While majority of people experience some sort of craving every now and then, for some people, food cravings can be a huge problem.

Why Cravings Are Problematic

Humans typically crave caloric-dense foods as opposed to nutrient-dense foods.

Caloric-dense foods are those that are usually high in sugar, salt or fat (basically, most highly-processed and fast foods).

Most people crave ice-cream, chocolate, crisps, or French fries. It's rare to hear someone longing for broccoli or a kale smoothie.

The problem is that these foods usually contain a lot of calories but have very little nutrients, if any.

As such, indulging in these foods often leads to imbalanced diets that don’t provide the body with the necessary nutrients it requires to thrive.

Additionally, because these high-calorie foods are usually highly palatable, giving in to these cravings can contribute to overeating, weight gain and obesity.

One study found that food cravings had a significant direct effect on body mass index (BMI) and may contribute to stress-related weight gain.

There’s also overwhelming evidence that links foods that are high in sugar, salt or unhealthy fat to various health conditions like diabetes, hypertension, and heart disease.

It’s, therefore, evident that cravings can be detrimental to our health if left unmanaged.

Understanding sugar cravings

To properly address cravings, it’s important to understand their underlying causes, that is, what actually goes on inside the body that causes cravings.

From a biologic view, there are 2 main pathways in the body that contribute to the overwhelming, often hard-to-resist, urge to want to eat sweet foods.

These 2 pathways happen in parallel, independent of each other, but they both work to augment the craving of sugar-containing foods.

Pathway 1: Taste receptors in the mouth

When you eat something sweet, the taste receptors in your mouth sense the sweet taste and send a signal to the brain.

The signal triggers activation of nerve cells in a part of the brain that leads to the release of dopamine.

Dopamine is a reward & motivation hormone. When present in the body, it not only produces the feeling of pleasure, but it also makes you to want to seek more of the thing that’s producing the pleasure.

Sweet taste is a powerful activator of dopamine release. The dopamine that’s released via this pathway then increases your desire for more of the sweet taste.

This is the reason why some people find themselves eating an entire bar of chocolate in one sitting even though they had intended to only eat a small piece.

Pathway 2: Post-ingestion effects of sugar

The pleasurable properties of sugar aren’t entirely due to it’s sweet taste. What happens after ingesting sugar-containing food also plays a role on whether you’ll want to eat more of it.

In the gut, carbohydrates and sweet foods are broken down into glucose, the form of sugar that’s absorbed into the bloodstream.

A group of nutrient-sensing cells in the small intestines detect the presence of glucose and send a signal to the brain via the vagus nerve.

This signal activates another part of the brain to produce dopamine that’s different from the one that’s activated by the taste receptors.

However, once the dopamine is produced, it produces the same effect — the desire (craving) to eat more foods that contain glucose.

Studies have shown that foods that lead to a sharp rise in blood glucose produce a more potent signal to the brain to produce dopamine than those that produce a moderate rise in blood glucose.

The rate at which dopamine is released has a huge effect on how much you’ll want to pursue more of what caused the increase in dopamine in the first place.

It then goes to show that a high-sugar-containing food that produces a sharp increase in blood glucose concentration will produce a rapid release of dopamine and a stronger craving to continue indulging.

So then, how do you control sugar cravings?

The good news is, from the knowledge of the underlying causes of these cravings, there are some science-based ways through which you can enjoy sweet foods without having to suffer cravings.

The main mechanism through which high-sugar foods produce cravings is by activating the release of dopamine in the brain.

Therefore, in order to blunt sugar cravings, you need to blunt the rate of dopamine release.

This can be done in two ways:

1. Eat sugar-containing foods with foods containing fiber, protein and/or healthy fats.

When high-sugar and carbohydrate-rich foods are consumed on their own or on an empty stomach, they cause a rapid increase in blood glucose, leading to what’s called a glucose spike.

However, emerging evidence suggests that when these foods are eaten after consuming food containing fiber (e.g. green salad), protein (e.g. eggs) and/or healthy fat (e.g. nuts or avocado), there’s a more moderate increase in blood glucose over time.

A moderate increase in blood glucose leads to a moderate rate of dopamine release and consequently, a lower craving response.

The graphs below show the differences in the rate of increase in blood glucose concentration after eating carbohydrate-rich and high-sugar foods alone and when combined with fiber (side salad) or healthy fat (almonds).

So, whenever you want to enjoy a sweet treat, eat it as a dessert after a meal in order to reduce the possibility of spiking blood glucose and developing cravings.

2. Limit intake of very sweet foods.

Remember, sweet taste alone is a powerful activator of dopamine release.

The sweeter the taste, the more strongly it triggers dopamine release encouraging overindulgence.

To avoid this, limit the intake of very sweet, highly palatable foods.

And on the few occasions that you do indulge, remember to first eat something that’s rich in fiber, protein and/or healthy fat.

Thanks for reading! I hope you found something valuable :)

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