So much for the low-carbohydrate lifestyle.

More than half of all U.S. consumers who have tried following diets that eschew carbs such as bread and sugar have given up, a survey released on Wednesday found, and interest in the popular regimens appears to have plateaued.

According to research firm InsightExpress, which conducted the survey online, fewer than 10 percent of Americans are currently on popular low-carbohydrate diets such as the Atkins, South Beach and The Zone.

In contrast, a survey conducted in December of last year by Opinion Dynamics Corporation found that, at the time, 11 percent of Americans were on low-carb diets.

The latest InsightExpress poll of 500 Americans also found that of survey participants who were not following low-carb diets, fewer than one in five would consider buying a low-carb product because they perceive a diet low in carbs to be unhealthy.

That’s unwelcome news for U.S. food companies such as H.J. Heinz Co. and General Mills Inc. that have scrambled in the past year to keep up with the low-carb trend by reformulating staples such as ketchup, cereal and yogurt to reduce their carbohydrate content.

In fact, Legg Mason beverage analyst Mark Swartzberg said on Wednesday that sales of mid-calorie colas recently introduced by both PepsiCo Inc. and Coca-Cola Co. “are either slow builds or something closer to dead on arrival.”

In a research note, Swartzberg said the findings were based on feedback from 51 U.S. retailers who had devoted shelf space to Coke’s C2 and Pepsi’s Pepsi Edge colas. The products, launched in June, were intended to appeal to calorie- and carb-wary consumers, reducing the sugar by adding Splenda, an alternative sweetener.