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Why does junk food make us happy?

Posted by. Dr Ben Morris
Posted on 13 February 2017


We perhaps all have an awareness that eating junk food is not the healthiest way to feed ourselves, yet we continue to consume it – presumably out of a strong sense of enjoyment.

Psychologist Dr Ben Morris from Leeds Trinity University looks into the issue of why we eat junk food and comes to the conclusion that junk food may actually make us feel happy.

On the most basic level, we eat food to fuel our bodies and the mechanism by which we determine if we are full or not is biological in nature. Junk food satisfies many of these hard wired biological needs, but how might this biological need translate into the psychological experience of happiness? Well the simple answer is that chemicals in our brain that are associated with happiness and sadness are also influenced to some extent by the makeup of food.

The experience of pleasure, a happy positive reward, is associated with a chemical in the brain called Dopamine. Many substances have an effect on Dopamine such as sugar, salt and fat, and from an evolutionary perspective were much sought after. Having access to a food source rich in these would represent a great survival advantage for the individual – and as such our 'psychology' was encouraged to seek it out.

Our brain is also hard wired to seek out variety when eating.  The ingredients in most junk foods are such that they trick the brain into satisfying the need for complexity. For example, think of the sensations we experience when eating a cheese burger and fries…the creamy brioche burger bun, sticky and savoury melted cheese, meaty burger pate, juicy tomato, crispy lettuce and salty fries. Sounds good right?

Foods that have complex textures are often viewed with great appeal. Think of the contrast in textures of a big plate of nachos versus a bowl of semolina. Research suggests that this complexity adds a variety to the eating process that can for some encourage further eating and feelings of pleasantness. These factors combine to present a satisfying profile for our taste buds that often leave us wanting more!

The salivary response is also key in the process of taste. When we first put food into our mouths and start to chew, we produce saliva which is the first stage in digestion. The more a food makes you salivate, the more it will cover your taste buds with flavour and this has a direct relationship to taste and enjoyment. Food types such as mayonnaise, ketchups, butters and salad dressings are particularly good at producing saliva, and as you might not be surprised – they are found high in many junk foods.

Of course, eating sweet, salty and fatty foods has been shown to influence taste and smell cues which make eating certain foods enjoyable. Research has pointed towards these sensory experiences being able to improve mood and reduce feelings of stress.

However, consume too much sugar on a regular basis, and this may affect your sense of control and ability to manage cravings, which is often a negative feeling. Since beverages such as fizzy drinks contain a lot of sugar not only does the Dopamine response encourage you to continue drinking, but will also affect your future cravings for sugar. The craving may create feelings of negative emotion which can only be alleviated by conceding to it. In a similar sense, a diet rich in salt and fat has also been associated with a similar Dopamine response.

Whilst having an understanding of what might underpin our desire for eating junk food is useful, let's hope this knowledge does not affect our relationship with a 'happy' aspect of many of our lives.