With more than 6 million copies in print, Dr. Atkins’ Diet Revolution is unquestionably one of the best-selling diet books of all time. The latest installment in a long line of tomes is Atkins for Life: The Complete Controlled Carb Program for Permanent Weight Loss and Good Health. Packed with recipes and menus, this book is geared toward folks who want to follow a lifelong, controlled carbohydrate plan to keep their weight stable. Numerous companion publications have been produced, including Atkins Diabetes Revolution: The Groundbreaking Approach to Preventing and Controlling Type 2 Diabetes, the last major book planned by Dr. Robert Atkins before his death.

It sounds too good to be true: Eat all the meat and fat you want and still lose weight. But small clinical trials show that Atkins does help peel off the pounds. What’s more, the regimen appears to help raise HDL cholesterol (the good kind) and lower triglycerides, another fat in the blood that is connected with risk of heart disease. One potential problem: the flood of low-carb foods—all typically high in calories—now on the market. Calories count, and gnoshing on too many “carb-free” snacks will only put the pounds back on.

Basic principles:

Fewer carbohydrates, more protein. Restricting carbs turns on the body’s fat-burning equipment, putting it into what the late Robert Atkins referred to as benign dietary ketosis (BDK). Simply put, this metabolic pathway, according to Atkins, is the one that breaks down stored body fat. When diets are high in carbs, the body burns them as fuel. But when carbs are restricted, the body must burn fat. Another key: lots of protein and fat. Atkins says these foods are satiating, and dieters are unlikely to binge on chicken, shrimp, or bacon.

How the diet works:

There are four phases. Proteins and fats are eaten liberally in every phase, but carbs are restricted to different degrees. In the first two weeks (the Induction phase) dieters are limited to 20 grams of carbohydrate per day, or roughly the amount in 3 cups of salad vegetables. After that, carbs are gradually added back in 5-gram increments until weight loss stops. Atkins calls this point the Critical Carbohydrate for Losing Level. Dieters will all have different thresholds, but about 35 to 40 grams of carbs per day seems to result in a continued 1-pound-per-week weight loss for the average person. As you approach your goal weight, you pass into the pre-maintenance and maintenance phases, in which carb levels, although still limited, are adjusted to suit your needs and preferences.

What you can eat:

Some news reports charge that Atkins has changed its position on protein, suggesting that dieters downsize on saturated fat and red meat. But the Atkins folks insist the plan hasn’t changed at all. It’s basically an eat-until-you’re-full regimen of pure proteins (meat, fish, eggs, cheese) and pure fats (olive oil, mayonnaise, butter, cream, sour cream). The key is controlling carbs, particularly in the initial two-week phase. Eventually, small amounts of carbohydrate-rich foods are added back into the diet. By the maintenance phase, you’ll be back to eating veggies and fruit again—though in controlled amounts.

Does the diet take and keep weight off?

Sure. But data is lacking about how long the pounds stay off. When it comes to other popular diets, there’s not much difference. Consider a recent Tufts-New England Medical Center study that pitted Atkins, Weight Watchers, The Zone, and Eat More, Weigh Less against each other. The result: Weight loss was between just 4 and 6 percent among all four groups, no matter what the plan.

Is the diet healthy?

Debatable. The Induction phase is highly unbalanced, with a mere 20 grams of carbohydrate per day. In the short term, you take off pounds, and blood lipids (cholesterol, triglycerides) seem to improve. But nutritionists balk at the high fat and saturated fat content of the steaks, chops, and other foods that Atkins promotes. Also unclear: the health impact of a lifetime of restricted carbs and high protein.

What do the experts say?

Registered dietitian Jane Kirby, author of Dieting for Dummies, second edition (Wiley Publishing Inc., 2004), gives the plan a thumbs-down. “Most nutritionists recommend that 55 to 60 percent of your calories come from carbohydrate,” Kirby says. “With a 1,500-calorie weight-loss diet, that would add up to 188 to 225 grams of carbs per day. Even the maintenance phase, which recommends 40 to 60 grams, is far too low.” Weight-loss researcher Gary Foster, Ph.D., of the University of Pennsylvania School of Medicine, admits he’s surprised by the fact that the Atkins diet, while successful at producing weight loss, doesn’t seem to raise the risk of high cholesterol and heart disease. “We thought that the harmful effects of a low-carb Atkins-style diet might be the high amounts of saturated fat,” says Foster, who recently published a one-year study comparing Atkins and a more traditional weight-loss diet. “And that turned out not to be true, at least at the one-year mark.” So Foster is working on a longer diet comparison study, this one for five years.

Who should consider the diet?

It’s a cakewalk for meat lovers and the vegetable-averse—at least temporarily. But how long can anyone eat a burger sans bun, or a steak without the potato?

Bottom line:

This one’s a puzzler. No nutritionist in her right mind would endorse a bonanza of high-fat, high-saturated fat foods like bacon, steak, cheese. It may take off the pounds, but it just doesn’t make good health sense, no matter what the early studies say.

Lead writer: Maureen Callahan, M.S., R.D.