It's long been lauded as the most important meal of the day.
And now the value of breakfast is back on the menu, with research showing the shocking effects of an unhealthy start to the day.
One study,
carried out at
Macquarie University in
Sydney, found that eating a high-fat, high-sugar breakfast for just four days could lead to significant brain changes.
These changes result in
learning and memory deficits similar to those seen in overweight and obese people.
One hundred and two lean, healthy people ate either a high-fat, high-sugar breakfast or a healthier alternative for four consecutive days.
Those consuming the unhealthy breakfast had a toasted sandwich and a chocolate milkshake.
The remaining healthier eaters consumed either a more nutritious variation of the same meal or a half portion of it.
Memory and learning tests were completed before and after breakfast on days one and four.
Results showed those who ate a fatty, sugary breakfast scored worse on the tests.
This is thought to be due to unhealthy breakfasts causing a spike in a person's blood sugar levels, which may impact their memory and cognitive function.
'Fluctuations in blood glucose levels may impair glucose metabolism and insulin signalling in the brain,' Dominic Tran, a postdoctoral research associate at the University of Sydney, wrote in
The Conversation.
Those who ate the sugary, fatty meal were also less able to distinguish between hunger and fullness. The study was published in the journal PLOS One.
This is thought to be due to the region of the brain that controls blood sugar levels, known as the hippocampus, also playing a role in appetite.
A separate
University of Oxford study produced similar results.
The research found that otherwise healthy adults who ate a high-fat diet for just five days also had impaired attention and memory function compared to those who had low-fat meals.
Sixteen men aged 19-to-28 ate either a high-fat, low-carb diet or a healthy eating regimen for five days. The diets were personalised to each participant and overseen by a dietitian.
The unhealthy eating plans were made up of 70 per cent fat, four per cent carbohydrates and 26 per cent protein.
This was compared to 50 per cent carbohydrate, 24 per cent fat and 26 per cent protein in the healthier diet.
Each morning, the men gave blood samples and completed cognitive tests.
Results showed the amount of circulating fat in the bloodstreams of the unhealthy eaters was 44 per cent higher than in the other participants.
Their concentration, speed of memory and ability to recall information also suffered.
The study was published in The American Journal of Clinical Nutrition.