Diets with a high intake of red meat and high in fat can have lasting effects on cognitive skills / Andrew Burton/Getty Images

In contrast nuts and leafy greens will make them sharper in later life

Fatty foods, processed meat and soft drinks will make you sluggish, more easily distracted and stunt your memory, an Australian study has shown.

Research carried out on over six hundred 14-year-olds found that those who had a “western diet” characterised by refined foods and meals high in carbohydrates scored lower in cognitive tasks at the age of 17.

The Western Australian Science Network reported that particularly diminished mental skills included “those involving reaction time/psychomotor function, visual attention, learning and memory”.

Chips and crisps were singled out for harsh judgement - their high consumption was significantly associated with longer reaction times on detection tasks.

In contrast, those who said at age 14 that they ate more nuts, fruit and leafy vegetables were found to perform better in the series of brain tests three years later.

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Dr Anett Nyaradi who carried out the study was quoted as saying that: “Adolescence represents a critical time period for brain development. It is possible that poor diet is a significant risk factor during this period…indeed, our findings support this proposition.”

While several factors are at play within the different diets, it is believed an overload of omega-6 in fried foods and red meat may unbalance metabolic pathways, causing a decline in thinking time.

Nyaradi claims the findings will have a great significance for future public health policies and  health promotion initiatives.