Atkins vs. South Beach: How do they measure up?

(Ediets) - Ever since the release of Dr. Atkins' Diet Revolution in the 1970s, so-called "low-carb" diets have been eating their way into mass consciousness.

While the merits of demonizing rice and potatoes are still questioned by a few traditionalists, notably the American Dietetic Association, low-carb eating is poised to stay: as many as 30 million Americans are giving it a whirl.

To help you understand the purpose of low-carb diets, and why they seem to work for weight loss, we compare two of the most popular and more reputable approaches – Atkins and The South Beach Diet.

The Plans

Philosophically, Atkins and South Beach hardly differ. Dr. Robert Atkins and Dr. Arthur Agatston emphasize that their respective diets are lifetime blueprints for healthy nutrition and disease prevention. Losing weight is almost an afterthought.

But both declare you'll lose plenty.

How? Advocates say it's the effects of highly refined carbohydrates (french fries, baked goods, cereals) on the body's blood sugar and insulin that cause weight gain. When you replace those carbs with fewer, healthier ones (mostly vegetables), blood sugar balances, insulin levels drop, and off come the pounds. The theory has its critics, but low-carbers cite supportive evidence. (And don't despair – you'll be eating more than vegetables!)

Atkins and South Beach begin with a strict two-week period of restricted carbohydrates that is virtually indistinguishable: No breads, pastas, rice, alcohol, sugar, etc. You eat meats, fish, and a few non-starchy vegetables.

In phase two, additional healthy carbohydrates are gradually reintroduced, such as fruits and whole grains. You stick to phase two on South Beach until you hit your weight goal. Then you're in the third phase, or "rest of your life" period. Dr. Atkins adds an additional step he calls "pre-maintenance," where weight loss is slowed as a transition to "lifetime maintenance."

"The biggest difference is in the structure," explains clinical nutritionist Jonny Bowden, clinical nutritionist and author of the just-released Living the Low Carb Life. (The book rates 14 of the fads and matches them with personality types.) "Atkins is very, very structured. Many people find that comforting, others find it restricting."

The Food

South Beach supporters like its laissez-faire approach to eating. The dieter is encouraged to experiment with a variety of food in her pursuit of low-carb options that work best for her. Desserts are permitted.

In dozens of recipes, both diets balk weight-loss tradition by calling for the consumption of animal and other fats. South Beach emphasizes lean cuts of meat.

"The Atkins diet advocates higher saturated fats in terms of animal protein than most physicians would recommend," says Dr. Louis Aronne, director of the Comprehensive Weight Control Program at Weill Medical College. "I honestly think [South Beach] is a somewhat better approach. We're finally starting to see that this diet has merit."

However, Colette Heimowitz, vice president of education and research at Atkins Nutritionals, Inc., says the Atkins Diet recommends a "balance and variety of fats," and she mentions olive oil, flaxseed oil, and others.

Regardless, both camps work hard to reverse the common misconception that low carb means "high protein." Protein is in balance, they say, with the vegetables, fruit and fiber they insist dieters not forsake.

To summarize, "There's difference in the details but they're both trying to teach us to ramp down the consumption of carbohydrates in junky processed foods and refined sugars and to build a diet around healthy proteins, good fats, lots of fiber, lots of vegetables and some fruits and nuts," says the nutritionist Bowden.

The Claims

Here's the part you've been waiting for. How much weight will you lose?

South Beach claims you'll shed a jaw-dropping 8 to 13 pounds in that first two-week period; Atkins makes no such claim. Both explain that pretty soon weight loss diminishes to the realistic (and healthy) one to two pounds a week expected on any weight-loss plan.

You will maintain your weight goal, too – so long as you incorporate the new eating habits for life. Which, both groups promise, will not be difficult: Unlike diets that emphasize low fat, you will not go hungry on Atkins or South Beach.

"You'll have three balanced meals a day, and it will be your job to eat so that your hunger is satisfied," Dr. Agatson writes on page one of The South Beach Diet. "Nothing undermines a weight-loss plan more than the distressing sensation that you need more food."

Additionally, say the doctors, your body chemistry will shift to eliminate cravings, vitality will return, and you will significantly reduce your risk for heart disease, hypertension, diabetes and other scary diseases – additional appeal worth considering.