take-out burger

Why Did I Just Eat That Again?

Forget the special sauce; it's actually a wave of environmental factors that's driving your persistent fast food cravings.


What we eat is a huge part of living a healthy lifestyle.  Often it’s hard to choose the right things.  When you’re tired after a hard day at work and all you want is that bag of chips that’s sitting on your counter.  When you don’t have the time to make lunch for the kids and yourself, so a slice of pizza from the work cafeteria has to be good enough.  When you just can’t say no to the ice cream that’s on sale.

But even if we have the best intentions, eating healthy can be an uphill battle.

It Ads Up

From a young age, TV commercials, internet ads, video games, or even packaging with branded logos or movie characters, teach us to crave foods high in salt and sugar.  A study from McMaster University, published last week in the journal Obesity Reviews, pulled together data from 29 trials with over 6000 children and found that shortly after seeing an ad for unhealthy food, children consumed more calories and had a preference for junk food.

Though parents play an obvious role in teaching their children to live a healthy lifestyle, it’s difficult to completely eliminate environmental influence, says Bradley Johnston corresponding author on the paper.

“In spite of [parents’] efforts to steer their children toward fresh fruits and vegetables, junk food ads still drive kids towards poor food and beverage choices.”  Johnston is an Assistant Professor at McMaster University and the University of Toronto as well as a clinical epidemiologist at the Hospital for Sick Children in Toronto.

Despite this, Quebec remains the only province to have banned food ads directed at children under the age of 13 in both print an electronic media.  This will hopefully change soon.

“To change minds and to change policies, decision-makers need quantifiable facts, our study has provided this,” says Prof. Johnston.


Even when we grow up and presumably have an easier time ignoring ads, the pressures don’t stop.  A study from the Dalla Lana school of Public Health at the University of Toronto found that people without diabetes had a 79% higher risk of developing the disease if they lived near a “fast food swamp” – that is an area with a high number of fast-food restaurants with few healthy options.

This was the first study in Canada to examine whether living within walking distance to various types of restaurants influences the risk of developing diabetes among adults.  Although the study did have information about the participants’ particular eating habits, diet is clearly a factor.

Importantly, it’s wasn’t just about the number of fast food joints, it was the lack of balanced options that made the difference.  This type of insight is invaluable to inform local government decisions on zoning policies.

“Policies that focus on the sheer volume (i.e. number) of fast-food outlets may not be as effective without also considering the overall balance or mix of outlets serving more and less healthful foods,” says PhD student and lead author Jane Polsky.

A vicious cycle?

And once we’ve gone down the unhealthy road, it might be harder to turn around again.  A recent study from the University of Manitoba found that overweight people have less gray and white matter in key areas of the brain.

According to state-of-the-art brain images, body mass index and body fat percent were associated with structural and functional differences in brain regions responsible for “cognition, reward processing and the ability to override impulsive behaviors.”  These differences may affect a person’s ability to lose weight or make healthy lifestyle choices, though it’s important to note that this study wasn’t designed to test causation.  That is, we can’t tell whether increased fat causes these changes in the brain or whether this brain composition predisposes a person to become overweight.

Future investigations can try to replicate the results using larger sample sizes and longitudinal study designs (following the same people over time) in order to observe changes and determined causation, says Chase Figley, Assistant Professor at the University of Manitoba and lead author of the study.

Don’t give up

Despite these roadblocks, we shouldn’t give up on the healthy thing.  For Prof. Figley, moderation is key.  “Eating your favorite comfort foods (e.g., hamburgers, french fries, cake, ice cream, etc.) is probably okay every once in a while; however, the key is to make these things the exception and not the rule.”

Educating yourself about environmental influences on diet is also important.  In fact, reading this blog post is already helping!  If you know you live in a “fast food swamp”, make a concerted effort to limit the number of times you eat out.  If you have young children, teach them about healthy food choices.  Draw their attention to those food ads so they actively think about them.

“Such awareness could build momentum toward shifting our food environment to one that better promotes and supports healthy eating. A food environment that makes the healthy choice not only the default choice, but also the preferred choice,” says Polsky.

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Malgosia Pakulska is a freelance science writer, speaker, and blogger. She completed her PhD in Professor Molly Shoichet’s lab studying drug delivery systems for spinal cord regeneration after injury. She is still passionate about research and wants to share that excitement with the public. When she is not in the lab, she is experimenting in the kitchen and blogging about it at Smart Cookie Bakes.