A recent research published by cannyminds. com, and undertaken in association with mental agility expert Tim Forrester, has claimed that mental exercises like crosswords and sudoku puzzles can burn up-to 90 calories per hour, which are much more than calories in a single chocolate chip cookie (56).

Exercising one's brain for an hour can also burn more calories than those contained in jammy dodger (85), a custard cream (57) or HobNob (79). According to the study, giving the brain a thorough workout dramatically increases the calories burnt by the body.

"Our brains require 0.1 calories every minute simply to survive. When we do something challenging such as a puzzle or a quiz we burn through 1.5 calories every minute", explained Forrester.

The study is based on the fact that neurons, in order to effectively carry out their function of transporting messages from the brain to the rest of the body, extract about 75% of glucose from sugar in the body, available calories and 20% of the blood's oxygen. Undertaking a stimulating mental exercise, however, leads to the brain extracting more glucose and calories from the blood to function at an increased speed.

The results of the study are backed by 8-time World Memory Champion Dominic O'Brien. "Just as you need to continually exercise your body to stay fit and healthy you also need to exercise your brain and memory to remain mentally agile”, he was quoted as saying.