I have heard sex isn't addicting, because someone can resist one night if they need to, but from experience a long time ago I'd say it just enhances your desire to do it again. Each time will make you want it again more, not less.Eating food makes those centers activate, as well. Anything that is pleasurable will make the same regions activate.
People with sex addictions have impulsive personalities they can't control. It's not because sex itself is addicting. Anything can be psychologically addicting if you're predisposed to addiction.