Food and Behaviour Research

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Beyond Obesity: Western Diet Shown to Make People Unintelligent

Ethan Huff

Junk food - Photo by Louis Hansel on Unsplash.jpg

Eating junk food doesn’t just make you fat — it also makes you stupid.


Findings from this study, involving teenagers from the general Australian population, support the proposal that diets rich in highly processed foods may impair healthy brain development and cognitive function.

It is important to note that purely observational studies like this one can never provide definitive evidence of cause-and-effect relationships - and so (as often happens), the dramatic media headline clearly overstates the findings from this particular study.

Nonetheless, these results add to a substantial and growing body of evidence that so-called 'junk-food' diets may have negative effects on mood, behaviour and cognition, as well as physical health.

This evidence includes some rigorously conducted randomised controlled trials - a study design that can provide evidence of cause and effect - showing that dietary supplementation with essential nutrients that are often lacking from modern diets - such as omega-3 fatty acids, and/or vitamins and minerals - can improve behaviour and some aspects of learning in both general and clinical populations. See:

More studies of this kind are still needed - but it already makes sense a priori to ensure that diets provide an adequate intake of all nutrients already known to be essential for healthy development of the brain and body.

This is important at any age - but it is particularly so during 'critical periods' of development. These include not only early life (when the brain is first forming and developing, and irreversible impairments caused by nutritional deficiencies have been well-documented) but also adolescence, as this period involves not only a rapid and transformative physical 'growth spurt', but also significant 'plasticity' and remodelling of the brain and nervous system at the same time - i.e. changes in brain structure and function in response to both hormonal changes and external environmental factors - including diet.

As the lead researcher notes, modern, western-type diets are rich in 'ultra-processed' foods, and typically fail to provide adequate amounts of the essential nutrients required for healthy brain development and functioning, including the long-chain omega-3 fats found in fish and seafood in particular, but also many vitamins and essential minerals.

Controlling as far as as possible for family and socioeconomic factors, the study found that teenagers whose diets at 14 years of age included high intakes of ultra-processed foods (and lower intakes of whole or minimally processed foods) showed significantly poorer performance at 17 years of age on several tasks from an age-standardised battery of cognitive tests involving memory, attention and visuo-motor coordination. 

For details of this research, see:


12 October 2014 - Epoch Times

Researchers from Australia came to this conclusion after evaluating the dietary habits of young teenagers as part of a large study, determining that those who consume a high amount of soft drinks, fried foods and other processed 'junk foods' perform worse mentally.

The University of Western Australia study looked at more than 600 kids who participated in the larger Western Australian Pregnancy Cohort (Raine) Study. Each of the participants, age 14 at the time, was asked to fill out a questionnaire about food frequency. Three years later, he or she was given a series of cognitive tasks to perform that evaluated performance compared to all the other children.

It was observed that children with higher consumption of takeout foods, processed meats, soft drinks and other refined and sugar-laden fare had decreased psychomotor function, impaired reaction time and problems focusing visually. Junk food eaters also had trouble learning and remembering things compared to those who ate more fruits and leafy green vegetables.

Junk foods, as most of our readers already know, lack the essential micronutrients and trace minerals typically found in whole foods. It is this general nutrient deficiency, says Dr. Anett Nyaradi, that more than likely causes junk food eaters to struggle cognitively.

Leafy green vegetables, for instance, are loaded with vitamins like folate, which has been linked to enhanced cognitive development. Whole, plant-based foods also tend to have a more balanced ratio of omega-3 and omega-6 fatty acids, which is extremely important for brain development. Junk foods typically contain excessive amounts of omega-6, and very little omega-3.

Unlike earlier nutrition studies, Dr. Nyaradi’s research looked at the health effects of comprehensive junk food consumption, not just isolated ingredients or nutrients. This holistic approach, she says, proves all the more how important it is for developing children to consume full-spectrum nutrition from whole, as opposed to processed, foods.

“Adolescence represents a critical time period for brain development,” she stated. “It is possible that poor diet is a significant risk factor during this period… indeed, our findings support this proposition.”

As far as omega-3s are concerned, children should be consuming plenty of foods and oils rich in this important brain nutrient. These include pastured meats and grass-fed butter, cod liver oil, skate liver oil, butter oil and hemp oil. The hemp and chia seeds are also highly beneficial brain foods rich in omega-3s