Atkins is well known and has been prominent since the late 1990s, but has diminished in popularity in recent years. Most people know how it works, eat plenty of protein and fat and stay off the carbs. We've tried it, and for a while it's fun, but you get the feeling this can't be good for your body, weight loss or no, and it's not a diet we'd not recommend using for more than a month or two. We haven't seen US numbers, but for comparison, at its peak in 2003, an estimated 3 million Brits had tried the Atkins approach, but by the end of 2004, Atkins book sales had plummeted tenfold.
The diet started back in 1963 when Dr. Robert C Atkins began to formalize his controlled carbs approach, in order to change the body pharmacy from a carbs to a fat burning machine. After a few days without carbs, the body goes into ketosis and you start burning fat as fuel instead. In theory, by cutting the carbs out, blood sugar remains more stable throughout the day. A useful monitor for the diet is to purchase a set of ketone sticks, so you can check your urine for ketone bodies to verify you're in ketosis.
Weight loss in the first two week period, the Induction Phase when you really minimize carbs, can be significant (up to 15 pounds but 6-10 is more typical). During this time the residual carbohydrates in your body are burnt off before you enter ketosis. Since carbohydrates are bound to water, a significant portion of this initial weight loss is just water and will reappear as soon as you eat carbs again. The diet change in the induction phase is huge--most of us eat 250 grams of carbs a day, and you will need to cut down to a mere 20g on Atkins.
After two weeks, you switch to the Ongoing Weight Loss phase of the diet, when you can eat a bit more carbs of the unrefined sort, increasing by 5 grams per day until you find your level for optimum weight loss, usually 25-50 grams. Once you get within 5-10 pounds of your goal, you move to Permanence phase, and then Lifetime Maintenance phase, where you're probably limiting carbs to 90 grams or so per day.
To be fair, there are many scientific studies showing that the diet does lead to weight loss, though many doctors also question the long-term health risks of staying on the diet. Many people (ourselves included) do suffer from headaches and light-headedness on it, as well as bad breath (from the ketones), insomnia, and nausea. With reduced fiber intake, constipation can also be a problem and there may be significant long term implications for the lack of fiber flushing your digestive system through. It may be worth putting up with the low-carb side effects for a couple weeks, but again, we wouldn't stay on this long-term. The high saturated fat intake may increase the risk of heart disease, and the unbalanced nature of the diet may lead to nutritional imbalances which could take years to manifest. Some doctors also suggest there may be long term risks to kidney and bone health. There is also concern that some of the weight loss will be from lean muscle mass rather than fat.
Menu: Cutting out the carbs means nothing sugary, no bread, rice, fruits, potatoes, pasta, alcohol, etc., though in the later stages you can have some veggies and such. You may be surprised by the level of carbs in some of your favorite foods. Instead, you can chow down without real limit on the normal no-no's of dieting - stuff like red meat, cheese, eggs, mayo, cream, butter, etc.
Prices: There is no organized Atkins program--you can buy the book for around $16 and follow it on your own without support or counseling.
There are many Atkins branded snacks, shakes, and meals, but these are pricey and there's really no need to pay a premium for these. Likewise, the Atkins fad has led many food manufacturers to prominently display the grams of carbs on their products, or promote them as "low carb," so finding Atkins-friendly fare in the supermarket is easy.