Many people of low to average weight are under the false impression that their weight is indicative of their health.

According to a study by the American Academy of Neurology, fatty and sugary foods are so harmful, they can damage your memory in four days.

Another experiment conducted at the University of Oxford showed you only need to eat a high-fat diet for five days to suffer from impaired attention and memory function, as well as mood swings.

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For many, being overweight isn't just about the struggle to find clothes that fit or confidence — it's common knowledge that it can affect your whole body.

The likelihood of strokes, heart attacks, and diabetes is much more likely the more you weigh, but that doesn't mean slim people can breathe a sigh of relief.

Being slim and being unhealthy aren't mutually exclusive - a low-quality diet or avoiding exercise can still put you at risk of diabetes, cancer, or a heart attack. YIUCHEUNG/Shutterstock

According to research published in both Circulation and The Lancet, it's clear that a healthy appearance doesn't necessarily mean you have a healthy body.

If you're slim but still have an unhealthy diet and avoid exercise, you're still at risk of developing diabetes, cancer, or suffering a heart attack.

However, if the risk of becoming overweight doesn't put you off reaching for that second bag of chips, perhaps you'll be slightly more inclined to put them down knowing that, according to new findings by the American Academy of Neurology, a diet that's consistently high in fat and sugar can lead to memory problems and diminished concentration.

Read more: Why closing your eyes and counting before meals may help you lose weight

An experiment conducted at the University of Oxford published in The American Journal of Clinical Nutrition indicated that you only need to eat a high-fat diet for five days to experience impaired attention and memory function, as well as mood swings.

A diet that's consistently high in fat and sugar can lead to memory problems and diminished concentration. Strelka/Flickr

This research is further supported by a study conducted by Macquarie University in Sydney, in which participants who ate a fatty and sugary breakfast for four days in a row showed similar cognitive problems to those exhibited by people who are overweight or obese.

The study actually found that people who ate high-fat, high-sugar breakfasts for just four days could experience significant brain changes, which can lead to similar learning and memory deficits seen in people who are overweight or obese.

A study published in Psychological Science showed that, even if chips or fizzy drinks are consumed frequently enough, similar symptoms can be experienced — fat and sugar raise your blood sugar levels, which, in turn, affects your glucose metabolism and your body's insulin production.