US sales of pork scratchings are booming, boosted by a health trend that encourages high-protein, low-carbohydrate snack food.

Thanks to advice from weight-loss gurus such as Dr Robert Atkins, whose diet regimen includes fried pig skin dipped in sour cream, pork rind sales grew 18 per cent last year - triple the growth rate of the snack-food industry as a whole. Dr Atkins' diet plan, and similar schemes such as the 'Zone' diet, contend that the energy catalyst insulin is the key to weight control.

By restricting carbohydrates, and thereby limiting the blood sugar that triggers insulin production, dieters are thought to be able to force their bodies to burn fat instead of fuel. That theory is thought to be largely responsible for the growing popularity of pork rinds. Figures just released by the Washington-based US Snack Food Association indicate that sales of the deep fried food rose faster last year than those for any other salty snack-food category except for beef jerky, totalling some $420m.

Old stalwarts such as pretzels and potato chips still dominate the $19bn snack food market. But pork scratchings have made impressive headway in recent years, and are now outselling such niche players as sunflower seeds and rapidly gaining on more traditionally popular products such as ready-to-eat popcorn. American industry watchers also credit the country's surging ethnic populations for some of the growth.

A favourite with consumers in mid-western and southern states, fried pork skins are known as chicharrones to Mexican Americans and Filipinos, who often top them with fiery salsa or spicy vinegar sauce. Inventive cooks also use chicharrones as an inexpensive meat substitute, or sprinkle the ground product over food for flavouring.

"It's the Filipino Parmesan, said Barry Levin, president of Snak King, whose pork-rind sales in the western United States have been expanding by some 30 per cent a year. "Ethnic consumers are a great market for us because they already know the product," added Levin.

Ohio-based Rudolph Foods, America's largest producer of pork rinds, recently elevated low-carbohydrate dieters to its list of prime target markets, based on feedback from retailers and consumers. The company has also introduced a new line of microwaveable pork rinds. "About 80 per cent of the e-mail we're getting right now is from women," said Rudolph spokeswoman Dori Coldwell. "And I'd say most of them are on that diet."

But pork rind manufacturers have yet to court weight watchers openly, or to change their labelling to highlight the product's high-protein and low-carbohydrate content, for fear of turning off core consumers.