But is it healthy to stay on this diet forever? That's what scientists are trying to find out.
One group of researchers has established a new registry of low-carb dieters. They began gathering names and data on people a year ago, and so far 2,300 carb-counting enthusiasts have signed on to the Controlled Carbohydrate Assessment Registry Bank Study (epi.aecom.yu.edu/ccarbs).
Preliminary data indicate that the low-carb participants, most of them women, eat about 1,800 calories a day, with 21% of calories coming from carbohydrates, 56% from fat and 23% from protein. More than half of the calories come from fat because of the high-fat content of foods like fatty meats, cheeses, butter and oils.
By comparison, the Institute of Medicine has recommended that the best diet for health is one that gets 45% to 65% of calories from carbohydrates, 20% to 35% from fat and 10% to 35% from protein.
The purpose of the study "is to look at the eating patterns of people who follow these diets long-term," says lead investigator C.J. Segal-Isaacson, nutrition scientist at the Albert Einstein College of Medicine in New York City.
The study is financed by the Atkins Foundation, which was established in 1999, four years before the death of cardiologist Robert C. Atkins, author of Dr. Atkins' New Diet Revolution and Atkins for Life.
Medical experts have long expressed reservations about the safety of the Atkins diet, a subject that resurfaced recently with a published report that Atkins was obese and had a history of heart problems when he died.
Researchers are investigating low-carb diets to see whether there are any serious health consequences. One large government-sponsored study is examining the diet's effect on weight, arteries, cholesterol, body composition, bones and kidneys.
Several short-term studies indicate that people lose weight on the programs without raising their overall cholesterol, and in fact they lower other heart-disease risk factors.
In the meantime, millions of people have either tried one of these diets or are on one now, and the number of low-carb grocery-store products, including brownies, bread and beer, is skyrocketing. Restaurant chains from Subway to T.G.I. Friday's boast low-carb offerings. There's even a new magazine focused on the lifestyle, LowCarb Living.
For some people, like Roseanne Clampet, 52, of Brooklyn, N.Y., watching carbs is not a new way to lose weight but a way of life that's getting easier now that low-carb dieting is going mainstream.
She started the Atkins diet in 1990. Her family thought she was crazy to follow what they considered a dangerous program.
Clampet lost 72 pounds on the plan in less than a year. And, except for a brief period, she has kept it off for 14 years by limiting carbohydrates, including desserts, bread, rice and pasta. She eats more beef, pork, chicken, fish, butter and full-fat salad dressing. At 5-foot-3, she weighs 133 pounds.
"It's not a daily struggle to maintain my weight. I enjoy the food I eat," says Clampet, an office manager for an advertising company in New York City. "Nothing tastes as good as being thin feels."
Diet has its detractors
Still, there are plenty of skeptics. Many nutritionists say the programs work for some dieters because they end up cutting calories, not because there is anything special about limiting carbs. They don't believe it will be easy for people to stick to the programs because the plans eliminate so many tasty and readily available foods.
Low-carb diets vary in specifics, but in general they cut some carbohydrates, especially starches and sugars. Many processed foods such as cakes, cookies, sodas and candy contain a lot of sugar and refined carbs and are no-no's.
The South Beach Diet, written by cardiologist Arthur Agatston, requires followers to stop eating most carbohydrates except for vegetables during the first two weeks of the program and then gradually add whole-grain bread, beans, oatmeal and fruit.
During the induction or first phase of the Atkins program, dieters are limited to 20 grams of net carbs (total carbs minus fiber) each day, which usually amounts to three cups of salad and a vegetable along with the meat dish. In this phase, dieters are getting only about 10% of their total calories from carbs.
The number of carbohydrates rises during the weight-loss and maintenance phases of the diets.
Once the dieter has lost the desired weight, the amount she can eat to maintain her loss varies, generally 40 to 100 grams of net carbs a day, says Colette Heimowitz, a nutritionist with the Atkins companies.
In practical terms, that means the dieter can eat more fruit and vegetables and a few more things such as whole-grain bread, a small potato or half a whole-grain bagel. But she can't eat half a pizza or a foot-long deli sandwich with chips and a cookie.
Beware of diet burnout
Many people become tired of the programs, which is evident by some of the compliance problems in studies so far, says George Blackburn, associate director of the division of nutrition at Harvard Medical School.
The diets cut out most of the grains and restrict fruits, which makes them monotonous, says Atlanta dietitian Chris Rosenbloom. She has found that many dieters quit, and those who stick with them make modifications so the programs work for them.
Michelle Nelson, 44, a nurse in Los Gatos, Calif., tried the Atkins diet for a month or two and lost some weight, but she found she couldn't face another hamburger or slice of bacon. She's among a group of people nicknamed low-carb refugees.
"I don't think you can eat limited foods like that the rest of your life," she says. "I wanted to eat from all the food groups. I wanted a bun on my hamburger and a baked potato with my steak."
She has been more successful with Weight Watchers (46 pounds in 10 months) because, she says, "it's balanced and healthy, and I don't feel deprived."
In any lifestyle program, you have to "learn variety and be creative with menus," Heimowitz says. "You can't eat the same thing all the time or you'll get bored, and you won't get all the nutritional components."
Some dieters who have followed low-carb programs for years say they aren't bored with the foods they're eating.
"I absolutely, positively do not feel my choices are limited," says Andrea Mondello, 42, of Poughkeepsie, N.Y. She has lost 100 pounds on the Atkins diet since 1999 and has kept it off except for a period of what she calls "emotional overeating." At 5-foot-2, she is 165 pounds, down from 265.
"I think it's what you get used to," says Mondello, a contributing writer for LowCarb Living magazine. "I don't deny it's an adjustment. After I got through the first few days of crabbiness, I was a different person."
Her cravings for carbs disappeared, and she stopped thinking about food morning, noon and night.
As with any weight-loss program, dieters have to pay attention to the details and can't expect miracles, Mondello says.
"Every day, you have to work to use your carb allotment with the healthiest ones you can. It's not easy.
"I eat more vegetables now than I ever did before. I eat meat, but I don't sit around and eat sausage and bacon all day. I try to eat as much fish as I can, but it's expensive. I eat lean cuts of pork and chicken, and I do eat steak sometimes."
The diet won't fix all your problems, she says. "If you have emotional issues that are causing you to overeat, they don't just disappear because you went on a low-carb diet."
Clampet says she misses coffee cake and other desserts. She has tried some of the new low-carb products, but they aren't close enough to the real thing. She thought a low-carb pasta was "gross. I didn't like it," and her response to one new meal-replacement bar was "yuck."
She'd rather splurge on the real thing.
"At this point, I can basically incorporate carbohydrates in my diet on a daily basis, but not to the extreme, not like cookies and chips, but on a healthy level. I can have a tuna sandwich on regular bread. I eat pasta and potatoes, but not a lot of them."
She recently attended a party that featured a huge buffet. She went for the meats and cheese and had only a few crackers.
"I don't think any diet is for everybody," Clampet says. "It's a matter of preference and what you can incorporate into your lifestyle."