Shocking new research has revealed that eating processed food for just four weeks can cause memory loss in rats.

The memory loss appears to be linked to massively increased levels of inflammation in the rats’ brains as a result of taking up the new diet.

Processed food: bad news for your brain

Processed food

Different groups of rats were fed a study diet that aimed to mimic ready-to-eat human foods that are often packaged for long shelf lives, such as potato chips and other snacks, frozen dishes like pasta dishes and pizzas, and deli meats containing preservatives.

The researchers randomly assigned 3-month-old and 24-month-old male rats to their normal chow (32% calories from protein, 54% from wheat-based complex carbs and 14% from fat), a highly processed diet (19.6% of calories from protein, 63.3% from refined carbs (cornstarch, maltodextrin and sucrose) and 17.1% from fat), or the same processed diet supplemented with DHA.

The researchers noted that, after four weeks on these diets, genes linked to a powerful pro-inflammatory protein and other markers of inflammation were activated at a significantly elevated level in the hippocampus and amygdala of the older rats that ate the processed diet alone compared to young rats on any diet and also older rats that ate the DHA-supplemented processed food.

Shockingly, the older rats on the processed diet showed signs of memory loss in behavioral experiments that weren’t evident in the young rats. They forgot having spent time in an unfamiliar space within a few days, a sign of problems with contextual memory in the hippocampus, and did not display anticipatory fear behavior to a “danger cue” (something suggesting danger, like a cat); this suggested abnormalities in the amygdala.

“The fact we’re seeing these effects so quickly is a little bit alarming,” said senior study author Ruth Barrientos.

“These findings indicate that consumption of a processed diet can produce significant and abrupt memory deficits — and in the aging population, rapid memory decline has a greater likelihood of progressing into neurodegenerative diseases such as Alzheimer’s disease. By being aware of this, maybe we can limit processed foods in our diets and increase consumption of foods that are rich in the omega-3 fatty acid DHA to either prevent or slow that progression.”

Previous research from Barrientos’s lab has already suggested that a short-term, high-fat diet can lead to memory loss and brain inflammation in older animals, and that DHA levels are lower in the hippocampus and amygdala of the aged rat brain.

DHA, or docosahexaenoic acid, is an omega-3 fatty acid that is present along with eicosapentaenoic acid (EPA) in fish and other seafood. One of DHA’s multiple functions in the brain is a role in reducing inflammatory response. This study is the first study of its ability to act against brain inflammation brought on by a processed-food diet, and will no doubt lead to further studies to better understand this role.

“The amygdala in humans has been implicated in memories associated with emotional — fear and anxiety-producing — events. If this region of the brain is dysfunctional, cues that predict danger may be missed and could lead to bad decisions,” Barrientos said.

The dangers of eating processed food

Here at Herculean Strength, we’ve been warning against the dangers of eating processed food since, well, the very beginning of the website. The figure above (taken from, for instance, shows how eating a processed food diet literally re-wired the brain of a doctor, as part of a BBC documentary on the negative effects of eating processed food.

Dr Chris Van Tulleken spent a month eating a diet that is now typical for a significant proportion of Brits, with 80% of all calories coming from processed food.

Writing about his experience in the Daily Mail, he said:

“A mere four weeks — that’s all it took for me to pile on enough fat to move from being a healthy weight to being overweight, putting my health at real risk. 

At the same time, my thinking became sluggish and I slept badly, lying in bed racked with anxiety, sweating with fears about everyday life. I developed heartburn as well as constipation. I got piles.

But worst of all, my brain rewired itself just as if I had developed an addiction to a drug of abuse. How did I wreak such terrible damage?”

Shockingly, the changes to his brain, which were revealed by brain scans, persisted after he gave up the diet!


The results of the new study also showed that DHA supplementation of the processed-food diets consumed by the older rats effectively helped to stave off the elevated inflammatory response in the brain as well as the behavioral signs of memory loss seen in the other rats who ate the processed-food diet.

All of the animals in the study had unlimited access to food. Both age groups gained a significant amount of weight on the processed diet, with old animals gaining significantly more than the young animals. It’s worth noting that DHA supplementation had no preventive effect on weight gain associated with eating highly processed foods.

That was a key finding: Barrientos cautioned against interpreting the results as a license for consumers to feast on processed foods as long as they take a DHA supplement. A better bet to prevent multiple negative effects of highly refined foods would be focusing on overall diet improvement, she said.

“These are the types of diets that are advertised as being low in fat, but they’re highly processed. They have no fiber and have refined carbohydrates that are also known as low-quality carbohydrates,” she said. “Folks who are used to looking at nutritional information need to pay attention to the fiber and quality of carbohydrates. This study really shows those things are important.”

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