Sweet potato noodle and turkey snack

If he weren’t an experienced chef, one might assume that Chad Robinson was, at heart, a practical joker. With a straight face, he’s demonstrating how to make pizza and ravioli -- without using any pasta or dough. Instead, thin slices of blanched and layered celery root do the job.

Robinson is one of a growing corps of chefs in Los Angeles catering to diners following high-protein diets.

Programs such as the Zone, Atkins and Sugar Busters have grown so popular, they’ve moved beyond the diet fringe and into the mainstream. Suddenly the world thinks carbohydrates are the enemy in the war on weight, not calories or fat. The only problem is, those evil carbs tend to be the very foods we crave most.

But cooking foods that will satisfy those cravings is a culinary challenge that requires real creativity. Two L.A. chefs who are doing it well are Robinson, the executive chef of Sunfare, an L.A. company that delivers meals based on the Zone plan; and Raj Brandston of Zone Gourmet in West Los Angeles.

With innovative substitutions for verboten ingredients, the chefs are attracting hundreds of customers willing to pay about $250 to $300 a week for breakfast, lunch, dinner and two snacks.

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Restrictions a creative challenge

The carbohydrate thing can make a chef’s life tough: forbidden is what many consider the staff of life -- bread, pasta and rice. Like many sensible weight-control plans, the Zone advocates the use of lean protein, low-carbohydrate grains, vegetables and fruits, and monounsaturated fat such as extra-virgin olive oil.

Like other high-protein plans, the Zone suggests that each meal contain 30% protein, 30% fat and 40% carbohydrates. Diets such as these have virtually demonized carbohydrates in the minds of Americans, and the marketplace has responded with everything from low-carbohydrate energy bars to a new low-carbohydrate beer, Michelob Ultra.

But some of the substitutions are easy: brown rice instead of white; steel-cut oats instead of instant; soy flour and protein powder in place of white flour; and turkey, chicken or fish instead of bacon and bologna.

Replacing unhealthful food with leaner ingredients isn’t the biggest challenge to most dieters, however. It’s the tedium of buying, measuring and cooking the same kinds of basic diet food.

The Zone’s restrictions might discourage many home chefs, and some low-carbohydrate cookbooks, including “Zone Perfect Meals in Minutes,” (Regan Books, 1997) by Barry Sears, founder of the Zone diet, don’t offer much for discriminating palates.

Recipes tend to rely on dried spices, prepackaged seasoning and sauce mixes or artificial products such as egg substitute.

But the restrictions have become a creative challenge to some chefs.

“If I’m handed a recipe, I say, ‘How can I clean it up and extract things that we aren’t supposed to use?’ ” Robinson said.

He has incorporated new cooking techniques, as well as ingredients. Unlike most commercial kitchens, Sunfare stocks nonstick cookware, trades longer cooking times for smaller amounts of oil, and often builds an entree beginning with the sauce.

“Most restaurants worry about getting food out quickly,” Robinson said. “They use higher heat and more oil.” His “low and slow” technique -- reducing the oil as necessary to cook -- allows him to create low-carbohydrate, lower-fat crumblike crusts for sauteed fish and chicken Parmesan, for example.

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Pasta and pizza stand-ins

After much experimentation, Robinson created his low-carbohydrate ravioli and pizza. To make a “ravioli,” disks of thinly sliced and blanched celery root are layered with mozzarella, smoked Gouda and seasoned ground chicken and topped with a final, cheese-sprinkled layer of celery root.

The result is surprisingly accurate: The celery root flavor fades and you’re left with just a pastalike texture.

He’s also created a nut-free pesto sauce -- basically, a standard recipe that omits the nuts and uses lime juice for a spike of extra flavor -- and a soft taco that wraps shredded chicken and salsa inside a “shell” of butter lettuce.

Brandston finds himself scouring L.A.’s vast ethnic groceries and restaurants for inspiration. He’s discovered sweet potato noodles in Koreatown that combine with spinach and eggs for a lighter egg foo young; created lasagna with slices of sweet potato standing in for the pasta sheets; and crafted a crepe batter by substituting soy flour and protein powder for the white flour.

Chefs know that eating bland or boring food isn’t going to keep most dieters happy. But when you can have your diet and your crepes too, there’s hope for more to come.