Certain proteins in eggs trigger wakefulness in cells in the brain, and not sugar.

Researchers at the University of Cambridge compared different actions of orexin cells that secrete orexin/hypocretin in the brain, which have been linked to narcolepsy and weight gain.

In an animal study, researchers found that amino acid nutrients found in proteins such as egg whites stimulate orexin neurons much more than other nutrients, while glucose(sugar) blocks orexin cells (which was cited as a reason for after-meal sleepiness).

"Sleep patterns, health, and body weight are intertwined. Shift work, as well as poor diet, can lead to obesity," said lead researcher Dr. Denis Burdakov of the Department of Pharmacology and Institute of Metabolic Science.

"Electrical impulses emitted by orexin cells stimulate wakefulness and tell the body to burn calories. We wondered whether dietary nutrients alter those impulses."

Protein meals can make people feel less calm and more alert than carbohydrate meals.

"What is exciting is to have a rational way to 'tune' select brain cells to be more or less active by deciding what food to eat," said Dr. Burdakov.

"To combat obesity and insomnia in today's society, we need more information on how diet affects sleep and appetite cells. For now, 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 study was published in the journal Neuron.