10 Harmful Effects of Junk Food on Mental Health

Check This article was edited and approved for accuracy By Adam Szmerling on February 14, 2022

Here’s an interesting fact.

Your brain never switches off.

Even when you are tucked up in bed at night, sleeping peacefully, your brain is still working away – priming your body for the day ahead. The brain has an incredibly high energy demand. In fact, despite only weighing 2% of your body weight, the brain uses about 20% of the calories you consume. It uses these calories to maintain things like your temperature, your breathing rate, your heart rate and your emotions.

Now, take a minute to reflect.

What exactly are you feeding your brain with?

The relationship between food and your mood

10 harmful effects of junk food - image of a lady and quote on junk food and effect on brain

The brain functions best when you feed it with high-quality foods full of fatty acids, nutrients and antioxidants that help to nourish and protect it.

Ultra-processed, sugary junk foods however, can cause inflammation in the brain and raise your risk of developing neurodegenerative and other chronic health conditions.

The food you eat primarily affects your brain via the gut. This makes sense considering the food you eat enters the gut rather than your brain. So, then, how do the messages encoded in food get from your gut to the brain?

Well, it largely comes down to your gut bacteria. The bacteria in your gut determines how well you absorb nutrients in your food and are responsible for activating neural pathways that establish communication between your brain and gut. In fact, your gut is responsible for manufacturing about 95% of the body’s serotonin – the feel good hormone. To put it simply, good food helps to establish a strong link to the brain and instructs to work on making you feel good.

Ultra-processed foods like packaged snack foods, buns and pastries, can hamper the production of those hormones that make us feel happy. Inflammation in the body that arises from poor food choices has been shown in several studies to lead to an increased risk of depression.

Aside from the long-term health concerns associated with unhealthy foods, processed foods can also have short term consequences on your mood. Sugary foods can spike blood sugar levels which can lead to a short burst of energy followed by a crash that’s associated with feeling tired and irritable.

Nutritional psychiatry is an area of research that has been growing over the past ten years. It focuses primarily on the science of the gut-brain connection. There are now hundreds, if not thousands of published articles that have established a relationship between junk food and a range of psychological issues (reference: diet and depression, diet and suicide)

Here are 10 science-backed reasons to avoid junk food:

1. Memory Problems

Junk food is high in saturated fat and sugar which can curb learning and memory. This has been observed among children where foods like Coca Cola and noodles were shown to negatively impact verbal memory.

2. Depression

Certain foods, when consumed in excess can bring significant changes to the neurotransmitters (or signalling messages) in your body so much that you become dependent on junk foods whenever you feel low. Junk foods can hamper the signalling of neurotransmitters such as dopamine and serotonin (the happy hormones). This can lead to depression and other mental health disorders.

3. Irritability

Canadian researchers have found that fast food can often result in people feeling more hurried or impatient. Julian House, one of the researchers from the above study says, “Fast food allows people to fill their stomachs as quickly as possible and move on to other things.” When you become used to instant gratification, you often find yourself becoming more impatient when things don’t come quickly. “Fast food allows people to fill their stomachs as quickly as possible and move on to other things.” When you become used to instant gratification, you often find yourself becoming more impatient when things don’t come quickly.

Infographic about the 10 harmful effects of junk food on your mind showing illustrations with junk food and a couple illustration on the top side and a handful of junk food and a woman looking depressed on the bottom side on a brown background and the Bayside Psychotherapy logo on top in the middle

4. You may end up splurging more

Sanford DeVoe, an associate professor at the University of Toronto’s Rotman School of Management, states that those people who begin to associate fast food with speed and instant gratification often spend more on food.

People who tend to eat junk food or fast food a lot splurge more than those who take the time to prepare meals.

5. Sugar Addiction

Junk foods often have a high sugar content, which can momentarily give you a boost of energy. The key word here, is momentarily. This rush becomes addictive because your body begins to adapt by suppressing dopamine and becoming reliant on sugar instead. According to Cassie Bjork, RD, LD, founder of Healthy Simple Life, sugar can be even more addictive than cocaine.

6. Anxiety

Unhealthy eating patterns are closely linked to feelings of anxiety and stress. Foods high in saturated fats, trans fats, and omega-6 fatty acids can cause inflammation while refined carbs can lead to fluctuations in your blood sugar levels. Small amounts of these fats are beneficial and necessary to optimize your brain’s functioning, but when consumed in excess, these all have been shown to increase feelings of anxiety.

Sugar and caffeine can also lead to short-term stress on the body, making your heart beat faster, your palms sweat, and your pupils dilate.

7. Hyperactivity

Sodium Benzoate in junk food can result in a pleasurable ‘high’, resulting in hyperactivity or feeling jittery. Over prolonged periods, these feelings can develop into severe mood swings.

8. Risk of dementia

Researchers at Brown University refer to Alzheimer’s disease as the diabetes of the brain. Fatty unhealthy foods can potentially increase insulin production in our body, resulting in type 2 diabetes. Insulin resistance has been shown to affect the creation and storage of memories, increasing the risk of dementia.

9. Mood Swings

Unhealthy eating habits can make you physically and mentally unstable while also causing irritability. You may think it’s a good idea to indulge in junk food when you’re feeling low, but researchers at Penn State have found otherwise. In their experiment, while there wasn’t any change (positive or negative) in the participants feeling good, those who felt down felt worse after indulging in junk food.

10. Lower self-control

Trans fats in processed foods can prevent your brain from actually understanding if you have eaten enough or not, resulting in lessened self-control.

Those who consume processed food are more likely to eat more. Several studies have shown this to be true. In one particular study, caloric intake increased by approximately 500 calories a day in the group following an ultra-processed food diet.

Remind yourself that healthy eating isn’t a hobby, it’s a lifestyle that needs commitment and dedication – but once you find consistency, it’s all worth it! You’ll look and feel better than ever.

When you start off on this journey, allow yourself the time you need to adapt to new nutritional choices. Trying to ditch everything at once might not work for you in the long run.

Sometimes it can help to speak to a professional therapist for junk food treatment. You can link up through a confidential and secure video conferencing session anywhere in Australia or call 03 9557 9113 for an appointment at our Melbourne clinic.

Professional help is just a click away. All you need to do is reach out.


Adam Szmerling

Bayside Psychotherapy was founded by Adam Szmerling in Melbourne, offering counselling and psychotherapy for individuals and couples. Adam's experience with psychotherapy inspired him to help others improve their self-understanding, mental health and wellbeing.

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