The number of U.S. consumers on low-carbohydrate diets rose sharply in the first two weeks of 2005, but many Americans are likely to give up the diets as the year progresses, according to a new survey.

In the week of Jan. 10, 15 percent of 1,000 Americans surveyed claimed to be following a low-carb diet such as Atkins or South Beach, according to market research firm Opinion Dynamics. The level is the highest since Opinion Dynamics began tracking low-carb dieting in December 2003.

A survey conducted a month earlier showed 6 percent of consumers claimed to be on low-carb diets, the firm said.

The popularity of low-carb diets, which shun foods like bread and pasta in favor of proteins such as meat and cheese, soared at the beginning of 2004 and prompted major U.S. food companies to make low-carb versions of everything from cereal to cookies.

The craze, however, had died down by the end of the year and sales of low-carb products slowed.

Larry Shiman, vice president of research for Boston-based Opinion Dynamics, said many consumers had taken up the low-carb regimens as part of a New Year’s resolution to lose weight.

“Some of these consumers will discontinue the diet as the year progresses,” Shiman said in a statement, adding that “it is clear that there is still strong consumer interest in low-carb diets.”