Scientists have found that egg proteins, specifically those found in the white, help us stay awake and feel alert.
They are much more effective than carbohydrates found in the chocolates, biscuits and sweets often relied on for a quick energy boost.
Cambridge University researchers looked at how nutrients affect the brain cells that keeping us awake and burning calories.
A mixture similar to the protein content of egg whites activated these cells, triggering the release of the stimulant orexin.
Sugar, however, blocked the release of orexin.
Researcher Dr Denis Burdakov said: "Research suggests that if you have a choice between jam on toast, or egg whites on toast, go for the latter."
"Even though the two may contain the same number of calories, having a bit of protein will tell the body to burn more calories out of those consumed."
The findings were published in the journal Neuron.
The slogan "Go to work on an egg" was used in a 1960s advertising campaign by the Egg Marketing Board.
More recently researchers for the British Nutrition Foundation, part-funded by the poultry industry, concluded that the type of cholesterol found in eggs has minimal effect on raising the risk of heart disease.
Previous research has shown that, contrary to popular perception, it is healthy to go to work on an egg.
