Panera Bread

(PNRA)

shares may come under pressure from investors Thursday, after the company reported an unexpected decline in same-store sales.

The St. Louis-based company said same-store sales fell 0.9% in the four-week period ended June 12. Company-owned stores fared better than franchises, with sales down 0.1% compared to a 1.3% decline.

Analysts were expecting a 1% increase, according to

Briefing.com

. Same-store sales rose 4.1% in the previous four-week period ended May 15.

The company operates bakery-cafes under the Panera Bread and Saint Louis Bread Co. names and, like

Krispy Kreme Doughnuts

(KKD)

, has been hurt by the low-carbohydrate diet craze. Panera shares hit a 52-week low of $32.65 in late May and closed at $38.11 Wednesday, well off their 52-week high of $47.79 touched last September.

The company launched six, new low-carb items earlier this month.

In May, the company said it earned $9.5 million, or 31 cents a share in its fiscal first quarter, vs. $7.5 million, or 25 cents a share, in the year-ago period. Same-store sales increased 1.8%. The company next announces quarterly earnings on Aug. 5.