Why do we crave junk food — and what can we do to adopt healthier eating habits?

Ultra-processed foods commonly contain five or more ingredients or additives, such as emulsifiers, sweeteners, preservatives or artificial colors. These give the food shelf-stability, make it look appealing, easy to digest and tasty. They are rich in pure sugar, high-fructose corn syrup, salt and the wrong types of fats. 

The reason that our bodies crave these foods is because they’re loaded with ingredients that tap into our brain’s pleasure centers, namely the dopamine reward pathway, the same one used by street drugs like cocaine. Dopamine is a 'feel-good neurotransmitter' which makes us feel better in the short term but reinforces the vicious circle of craving food again.

Among the foods we crave, some are loaded with carbohydrates, which can boost serotonin. Serotonin is another neurotransmitter called the ‘happiness hormone’. 

Moreover, ultra-processed foods also interfere with the signaling of a third neurotransmitter called leptin, which aims to tell our bodies that we should stop eating. If we consistently consume ultra-processed foods, leptin will simply stop working. We then run the risk of developing what is known as leptin resistance, which can lead to overeating. 

In the short term, consuming these foods may make us feel good, but that's just a temporary mood boost with long-term health consequences.

Ultra-processed foods are associated with poor health outcomes. They negatively impact our gut microbiome and increase the risk of colon cancer. There are also harmful substances produced during the manufacturing process of ultra-processed food. This includes acrylamide and advanced glycation end products, which are released from foods during high-temperature cooking. Both are known carcinogens. 

According to a study published in the British Medical Journal and covering the period 2009-2023, increased consumption of ultra-processed foods led to a 50% rise in cardiovascular deaths and a 12% jump in Type 2 diabetes. In addition, anxiety diagnoses rose by 48% and mental disorders, including depression, by 53%. There is less convincing, yet highly suggestive, evidence of a 21% increase in all-cause mortality. The risk of poor sleep increased by 41%, wheezing by 40% and, unsurprisingly, obesity by 55%.

What can we do?

Here are a few ideas. Substitute your sugary or diet sodas and energy drinks with sparkling water or unsweetened tea. Check labels and choose foods with fewer ingredients. Stay away from foods whose ingredients you don't recognize. A good first step would be to eat an orange instead of store-bought orange juice, which has had the fibers removed and often sugar added. Eating whole foods means more fiber in your diet, which not only makes you feel full, but also reduces cravings. Ensuring you are sufficiently hydrated is another simple step. Our brains often mix up hunger and thirst centers. So instead of eating junk food, drink a glass of water. 

A number of studies have shown that cutting down on ultra-processed foods in your diet has considerable health benefits, even after just two weeks. By making it a habit to pick healthier foods, you can achieve significant health and wellness benefits over the long term.