The average Canadian adult consumes more than triple the daily limit of 25g added sugar recommended by the World Health Organization. (Unsplash/muhammad ruqiyaddin), CC BY-SA

Amy Reichelt, Western University

We love sweet treats. But too much sugar in our diets can lead to weight gain and obesity, Type 2 diabetes and dental decay. We know we shouldn’t be eating candy, ice cream, cookies, cakes and drinking sugary sodas, but sometimes they are so hard to resist.

It’s as if our brain is hardwired to want these foods.

As a neuroscientist my research centres on how modern day “obesogenic,” or obesity-promoting, diets change the brain. I want to understand how what we eat alters our behaviour and whether brain changes can be mitigated by other lifestyle factors.

Your body runs on sugar — glucose to be precise. Glucose comes from the Greek word glukos which means sweet. Glucose fuels the cells that make up our body — including brain cells (neurons).

3D illustration of neurons in human brain. (Shutterstock)

Dopamine “hits” from eating sugar

On an evolutionary basis, our primitive ancestors were scavengers. Sugary foods are excellent sources of energy, so we have evolved to find sweet foods particularly pleasurable. Foods with unpleasant, bitter and sour tastes can be unripe, poisonous or rotting — causing sickness.

So to maximize our survival as a species, we have an innate brain system that makes us like sweet foods since they’re a great source of energy to fuel our bodies.


Read more: Forget toast and oatmeal, low-carb breakfasts reduce sugar spikes in those with Type 2 diabetes


When we eat sweet foods the brain’s reward system — called the mesolimbic dopamine system — gets activated. Dopamine is a brain chemical released by neurons and can signal that an event was positive. When the reward system fires, it reinforces behaviours — making it more likely for us to carry out these actions again.

Dopamine “hits” from eating sugar promote rapid learning to preferentially find more of these foods.

Our environment today is abundant with sweet, energy rich foods. We no longer have to forage for these special sugary foods — they are available everywhere. Unfortunately, our brain is still functionally very similar to our ancestors, and it really likes sugar. So what happens in the brain when we excessively consume sugar?