The low-carb craze was good to nut processor John B. Sanfilippo (NASDAQ:JBSS) and its Fisher line of products. But now that the age of Atkins is well behind us, Wall Street is cracking down on the company's shares. Is there a buying opportunity here?

In the heady days when Fisher nuts were touted as a carb-free source of protein, Sanfilippo stock rose 9.3 times in value in 20 months. Since that peak, the company's stock has shed three-quarters of its value. Just today, the stock hit a new 52-week low, losing one-fourth of its market cap.

The Nov. 1 release of the company's latest operating results contributed to its crushing share price. Although sales increased 2.6% over the year-ago quarter, net income fell from a profit of $0.24 to a loss of $0.14 a share. Analysts were expecting a $0.26 profit! A 13% net sales increase at the flagship Fisher brand was not enough to offset an 8% decline in the overall consumer channel, where private-label customers refused to accept the company's price increases.

Unfortunately for nutty investors, the Planter's Nuts division of Motley Fool Income Investor recommendation Kraft Foods (NYSE:KFT) has priced its branded products so low that private labels aren't noticeably cheaper. So, the logic goes, until nut prices fall (which will not happen until next year at the earliest) and/or the division's able to eke out increases in volume, the private-label segment will remain weak.

The news gets worse. Due to higher short-term debt levels and its net loss, the company is warning that it may violate a financial covenant in both its short-term and long-term credit facilities in coming months.

While it seeks covenant waivers, investors only have two morsels of good news to savor. Fisher is gaining market share, and indications are that cashew, pecan, and peanut prices could decline next year and revive the private-label business.

The company is headed into its peak holiday selling season. That would normally be good news, but listen to the conference call. Without the private-label business recovering, earnings are going to be squeezed once again -- I'd say the stock is nothing more than a speculative play until the company can work through its current problems.

Egg king Cal-Maine (NASDAQ:CALM), specialty wheat producer MGP Ingredients (NASDAQ:MGPI), and meat protein powerhouse Tyson Foods (NYSE:TSN) all turned heads during the diet fad. Their stocks have subsequently fallen. Commodities, as always, are proving to be a tough nut to crack.

Looking for more companies like Kraft that pair delicious dividends with mouth-watering, market-beating returns? Snack on a free 30-day trial subscription to Motley Fool Income Investor .

The Motley Fool has kicked off its ninth annual Foolanthropy campaign! Nominate your favorite charities on our Foolanthropy discussion board through Nov. 6. For guidelines on what makes a charity Foolish, visit www.foolanthropy.com .

Fool contributor W.D. Crotty does not own shares in any of the companies mentioned, although writing about John B. has made W.D. ready to crank up the Beach Boys' "Sloop John B." Click hereto see The Motley Fool's disclosure policy.