Dec. 1: Working out at the gym everyday could lead to a physical addiction to exercise, according to a study.

Scientists have discovered that the parts of the brain involved in drug, drink and gambling cravings may also become over-active when ke- ep-fit fanatics are deprived of exercise.

The findings may settle the long-running debate about whether exercise addiction is a physical or psychological phenomenon.

Exercise addiction is diagnosed when exercise becomes the focus of the day and takes priority over family, work and relationships. In extreme cases, addicts suffer depression, sleep problems and anxiety.

Psychologists say exercise addiction is rare but may be on the increase.

A new animal study, published in Behavioural Neuroscience, suggests that the problem may be physical not psychological.

A team led by Dr Justin Rhodes, of Oregon Health and Science University, studied the brain activity of two groups of mice deprived of exercise wheels. One group were normal laboratory animals, the others had been bred for their love of running.

Rhodes said: “All mice run on wheels and, therefore, have a motivation to run.” But the specially bred mice had a gen-etic predisposition to run longer distances.

“They may represent those few extreme individuals in the population with an intense desire or compulsion to run,” Rhodes added.

Over six days the normal mice ran about two miles while the specially bred mice managed six miles.

On the seventh day, half the mice in each group were removed from the exercise wheel. All mice denied exercise had higher levels of brain activity in 16 out of 25 brain regions. The activity was highest in the specially bred mice.

“In the high running mice, certain brain regions displayed extremely high levels of activity,” said Rhodes.

“These were the same brain regions that become activated when you prevent rats from getting their daily fix of cocaine, morphine, alcohol or nicotine,” he added.

The findings by the scientists suggested that the mice had a physical craving for exercise if prevented from running. People may have a similar reaction to exercise, the team believes.