Can Junk Food Shrink Your Brain?

Junk Food Brain EffectsDid you know that increasing or even maintaining your intake of burgers, fries and soda pop—and pretty much any other hallmark of the “Western diet,” high in saturated fats and refined sugar—isn’t just an efficient way of rotting your teeth out and raising your risk of cancer, diabetes or heart disease, but that you may also be shrinking your brain?

A recent study posted on BMC Medicine suggests as much.

While you’re putting away all the junk food or opting out of broccoli and Brussels sprouts, your hippocampus (a brain structure responsible for learning, memory, mood regulation—and what has been tied to depression) is getting smaller, specifically on the left side of your brain.

The new research comes out of Australia, through the Personality and Total Health Through Life Study. The study used a sample of 255 adults, aged 60-64 years old at the start, and which ran for four years.

Participants completed food frequency questionnaires and received two brain imaging scans, magnetic resonance imaging (MRIs), at the beginning and at the end of the study.

Individuals indicated their consumption frequency of foods from two types of diets: 1) the “prudent,” or healthy diet, which consisted of fresh vegetables, salad, fruit and grilled fish; and 2) the “Western,” or unhealthy diet, made up mostly of roasted meats, sausage, hamburgers, steaks and chips (or French fries) and crisps (called chips by American fast-food counterparts) and soft drinks.

From the results of the study, researchers found that eating unhealthier foods as well as abstaining from a healthy, nutrient-dense diet were both associated with a smaller left hippocampal volume. In fact, the difference in hippocampus volume between participants who ate a healthy and unhealthy diet was 203 cubic millimeters, which was 62 percent of the average decline over a 4-year span (the length of the study).

Researchers’ findings suggest dietary intervention as a way to “promote hippocampus health, decrease age-related atrophy, and prevent negative health outcomes” associated with that atrophy (e.g. poorer mental health outcomes in clinical settings and greater risk of depression).

So does this mean that you should fret over every French fry? Be wary of any more than a slice (or a little bite) of cheesy, perhaps pepperoni-laden pizza?

Well, the less frequently you consume these foods, if at all, the better; and whenever you do eat them, portions should be substantially smaller than what is considered average or “normal.”

Exercise and caloric restriction (in a healthy way—that is, without depriving oneself of important macro and micronutrients) are also ways to promote neurogenesis, the generation of neurons, in the hippocampus.

With strong new evidence supporting a poor diet’s role in promoting mental disorder, cognitive decline, depression and dementia, and a simultaneous worldwide shift toward fast foods and sugary drinks, it’s more important now to understand—and act on—the fact that these poor diet choices are not just affecting our bodies, instigating obesity and disease, but diminishing our minds.


Western diet is associated with a smaller hippocampus: a longitudinal investigation. Felice N. Jacka (1,2,3,4), Nicolas Cherbuin (5), Kaarin J. Anstey (5), Perminder Sachdev (6), and Peter Butterworth (5)

1 Division of Nutritional Psychiatry Research, IMPACT Strategic Research Centre, Deakin University, Geelong, Australia

2 Department of Psychiatry, The University of Melbourne, Melbourne, Australia

3 Centre for Adolescent Health, Murdoch Children’s Research Institute, Melbourne, Australia

4 Black Dog Institute, Sydney, Australia

5 Centre for Research on Ageing, Health and Wellbeing, Research School of Population Health, The Australian National University, Canberra, Australia

6 Centre for Healthy Brain Ageing (CHeBA), School of Psychiatry, Faculty of Medicine, University of New South Wales, Sydney, Australia