August 18, 2009

Those who run the hardest may get addicted

Exercise is always being advised for good health but a study in rats found extreme exercise may be physically addicting, U.S. researchers found.

Lead author Robin Kanarek of Tufts University said excessive running shares similarities with drug-taking behavior.

As with food intake and other parts of life, moderation seems to be the key, Kanarek says in a statement. 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.

The study involved 44 male and 40 female rats that were allowed either to run in exercise wheels or remain inactive.

To simulate anorexia athletica -- exercise addiction -- the researchers divided the active and inactive rats into groups whose members were either given food for one hour a day or around the clock. Rats in all four groups were then given naloxone, a medicine for heroin overdose that produces immediate withdrawal symptoms.

The study, published in Behavioral Neuroscience, found active rats showed withdrawal symptoms like those seen in narcotics addicts, while the active rats who had access to food for only one hour a day both ran the most and displayed the most severe withdrawal symptoms.