Junk food can make your memory worse in just 4 days, says study

A new study shows junk food doesn’t just harm your body — it can affect your memory in days. The good news: early lifestyle changes may reverse the damage. (Image: Pexels)

Junk food is notorious for causing various health issues in your body, but a new study shows it could negatively impact your mind too. According to scientists from the University of North Carolina (UNC), just four days on a high-fat diet, that may include burgers, chips, and all the usual suspects, can cause memory problems. Nevertheless, switching your diet or even brief fasting could help your brain bounce back.

In the study led by UNC professor Dr Juan Song, researchers discovered that a key part of the brain involved in memory,  the hippocampus, reacts almost immediately to fatty foods. Special brain cells called CCK interneurons became overactive after just four days on a high-fat diet in mice. These cells help regulate memory, and when they go into overdrive, memory suffers. This isn’t about long-term damage from years of unhealthy eating, the effect was almost instant.

The study, published in Neuron, focused on how short-term exposure to junk food affects brain activity. It revealed that:

• A high-fat diet reduces the brain's ability to process glucose, its main energy source.
• This drop in glucose availability made memory-regulating neurons hyperactive, which disrupted memory.
• Just four days of eating food high in saturated fat was enough to impair memory in mice.
• Restoring glucose levels through fasting or diet shifts helped calm the brain and restore memory. Also Read: Neurologist warns against three common foods that could harm brain health

The hippocampus is like the brain’s memory centre. The study found it reacts quickly to high-fat foods, not over months or years, but in just days. These changes happen before any visible weight gain or signs of diabetes.

Fatty food reduces brain energy

Junk food makes it harder for the brain to access glucose, which it needs to function properly. Without enough glucose, certain neurons go into overdrive, causing confusion in memory circuits.

The problem protein

The study also highlighted a protein called PKM2, which controls how brain cells use energy. This protein gets disrupted by poor diet, adding to the memory issues.

Why this matters for long-term health

The research links high-fat diets with possible early triggers of neurodegenerative diseases like dementia and Alzheimer’s. But it also shows that early intervention — especially dietary, could stop or even reverse the damage. “This work highlights how what we eat can rapidly affect brain health,” said Dr Song. “With early lifestyle changes like fasting or cutting back on junk food, we may be able to protect memory and reduce the growing burden of dementia tied to obesity and metabolic problems.”

Also Read: 8 vitamin B12-rich foods you should eat for your brain health

Prevention tips: 

The researchers found that intermittent fasting or simply switching back to healthier foods helped restore brain function. It calmed overactive neurons and improved memory. Dr Song said, “With early lifestyle changes like fasting or cutting back on junk food, we may be able to protect memory and reduce the growing burden of dementia tied to obesity and metabolic problems.”

FAQs on the link between brain health and food:

How does diet impact brain health?
Diet impacts brain health by influencing the availability of glucose, the brain’s main energy source. High-fat diets can reduce glucose processing, causing memory-regulating neurons to become hyperactive, which disrupts memory.

Can junk food cause immediate brain issues?
Yes, the study found that just four days on a high-fat diet could impair memory almost instantly due to the overactivity of CCK interneurons in the hippocampus.

Is it possible to reverse the negative effects of a high-fat diet on the brain?
Yes, restoring glucose levels through dietary changes or brief fasting can help calm the brain and improve memory, potentially reversing the negative effects of a high-fat diet.

Disclaimer: This article, including health and fitness advice, only provides generic information. Don’t treat it as a substitute for qualified medical opinion. Always consult a specialist for a specific health diagnosis.