Do you feel different after eating fast food? A physical change may be obvious, but what about a mental shift?

New research published in Royal Society Open Science verifies that eating a "Western-style diet" rich in saturated fat and added sugar can impair brain function. The effects were noticed after only eight days.

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The claim that a Western-style diet can rapidly impair functions of the hippocampus has long been proven on animals. However, the new February 2020 study charts findings tested on 110 healthy, lean adults recruited from Macquarie University.

Each participant was screened before enrollment to take place in the 8-day study, and the pre-screening ensured subjects were "lean, healthy and currently consuming a nutritious diet." The final group covered 17-35 year-olds with a BMI of 17-26.

Starting with a healthy base, one group was put on a "Western-style diet" for one week. This short bout of experimental exposure had profound results.

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Along with "adverse neurocognitive effects," eating a predominantly Western-style diet significantly impaired appetite control- a function that can lead to overeating and eventually weight gain and other health-related issues.

After reading the study, we were most interested in three things:

1. What exactly did these subjects eat?
2. How did it change their brains?
3. How can we make sure this doesn't happen to us?

Let's dig into the meat of these questions...

What Did Subjects Eat?

Or should we say, what constitutes a Western diet?

western diet

Researchers say this type of diet is rich in saturated fat - i.e. fatty cuts of beef, dark poultry, cakes, pastries, and high-fat dairies like butter, cheese, and ice cream. The diet is also high in added sugar - i.e. cakes, candy, cookies, and sodas.  

On Days 1 and 8 of the study, the Western-diet group was served a breakfast of a toasted sandwich and high-fat, high-sugar milk shake.

If that meal seems unrealistic, think of a typical breakfast order at a coffee chain; A toasted sandwich or bread and sugar/cream-filled coffee shake.

On the other days of the study, subjects were instructed to eat two Belgian waffles for breakfast or a dessert (Days 2-7). Also during those four days, they would need to eat a meal + drink/dessert from a popular fast-food chain.

Apart from these instructions, participants could stick to their normal "healthy" diets. Remember, each person was pre-screened as a generally healthy eater.

western-style diet

By these parameters, a "Western-style diet" consist of such high saturated fat and added sugar foods like waffles, milk shakes, sugary drinks, desserts, and a couple of drive-through meals a week.

You might already be comparing this to your regular diet. And you wouldn't be crazy to think it seems like a somewhat normal, realistic diet. Almost half of US adults aged 20-39 consume fast food once a day.

How Does This Food Change The Brain?

When animals are fed a Western-style diet, they quickly demonstrate rapid impairments to the hippocampal function. The same occurred with humans in this study.

Quick anatomy lesson. Let's get acquainted with the hippocampus- the area of the brain damaged by a Western-style diet.

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This complex brain structure sits deep in the temporal lobe and gets its name from the Greek word for sea monster, given its similarity in shape to a sea horse. The major role played by the hippocampus is in learning and memory, although it moonlights as a support for spatial navigation. The hippocampus can be damaged by different stimuli and is affected by certain neurological and psychiatric disorders such as chronic stress and Alzheimer's disease.

In this new study, researchers measured hippocampal-dependent learning and memory (HDLM) and appetite control levels before and after the trial.

They found the diet in question to have adverse neurocognitive effects while impairing appetite control, suggesting that the hippocampus and its health may directly affect appetite control and food cues processed by the brain.

In the end, the study suggests Western-style food changes the brain by impairing HDLM while making us want to eat more despite being full.

How to Stop This From Happening to Us?

Perhaps the most concerning finding of the new study was how quickly an adverse effect can be noticed after eating a Western-style diet. Researchers write " One week's exposure to a WS-diet caused a measurable weakening."

Given the temporal limitation of the study, researchers did not observe whether this exposure could be remedied. However, if we look back to animal studies using short-term Western-style diets there is evidence that impairments caused by this eating style are reversible.

healthy ray j GIF by MTV Cribs

This means we all have a choice to move toward healthier brain function and appetite control and away from, well, cheeseburgers-fries-and-a-shake.

One way to ensure your diet does not have an adverse effect on your mental and physical health is to simply track what you eat and slowly replace saturated fats and high-sugar items with real, whole foods abundant with nutrients.

In this case, food really is the best medicine.

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