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What: GNC Holdings' (GNC) woes continued today as its CEO stepped down and the company suspended its guidance after another weak earnings report. As of 12:26 p.m. EDT, the stock was down 20.5%.

So what: The health and wellness retailer's streak of declines in same-store sales continued as comps fell 3.7% in the second quarter. Adjusted earnings per share increased from $0.77 to $0.79, which beat estimates by a penny, though reported revenue missed expectations.

The results were in line with recent quarters, but the resignation of CEO Mike Archbold and appointment of Director Robert Moran as interim CEO seemed to indicate more trouble at the nutritional-supplement specialist. Moran acknowledged the company's problems, saying, "Our results for the quarter were disappointing," and added the company must work to reverse current trends. He also said the retailer would continue its review of strategic and financial alternatives, which may indicate a future sale.

Now what: GNC also said it would suspend its share buyback program, which had been helping prop up earnings per share as shares outstanding fell 20% over the past year.

Management scrapped its full-year guidance, but Moran insisted that the company was just as focused on delivering improved performance, saying, "We remain confident in GNC's long-term prospects."

Still, the company's challenges may be outside its control. With over 9,000 locations worldwide and 6,700 in the U.S., GNC seems to have saturated a market that has become ripe for disruption by e-commerce. Rival Vitamin Shoppe (VSI) has also seen comparable sales drop recently, indicating an industrywide trend. With ample profits and a low valuation, GNC could be an appealing target for a private-equity buyer, but I wouldn't expect a meaningful recovery in the overall business.