Researchers at Tufts University conducted the study, which has been published in the August issue of the American Psychological Association’s journal Behavioural Neuroscience.
The researchers divided rats into groups and gave them a drug called naloxone, which is used for heroin overdose and causes withdrawal symptoms in addicts. One group of rats was highly active, the other group inactive. The highly active group of rats showed withdrawal symptoms like those seen in narcotics addicts, while inactive and moderately active rats did not show such symptoms. The worst symptoms were seen in the rats that ran the most. The researchers concluded that the excessively active rats seemed to have undergone similar brain changes as rats addicted to drugs.
Exercise, like addictive drugs, is known to release neurotransmitters including endorphins and dopamine, which are part of the brain’s pleasure and reward system. The research findings are particularly relevant to a potentially fatal eating disorder known as anorexia athletica. In anorexia athletica, people trying to lose weight through exercise become compulsive about physical activity, in a similar manner as drug addicts become compulsive about taking drugs.
It is important to note that there is no evidence that moderate exercise is harmful or addictive. "As with food intake and other parts of life, moderation seems to be the key. Exercise, as long as it doesn't interfere with other aspects of one's life, is a good thing with respect to both physical and mental health," said lead author Robin Kanarek, PhD.
In fact, the researchers note that moderate exercise, which also stimulates endorphins and other “pleasure chemicals” in the brain but without becoming addictive, could be incorporated into treatment for drug addicts.
