ACNielsen U.S., an operating unit of ACNielsen Corporation (NYSE: ART), announced today during the National Association of Convenience Stores annual convention that its Convenience Track(TM) service has begun monitoring sales of energy bars sold in convenience stores. "Energy bars have made a successful transition from products sold primarily in health food stores to products that can now be found in most grocery, drug, mass merchandise and a growing number of convenience stores," said Scott Keplinger, ACNielsen vice president, retail measurement services.