Ah yes, the forever changing field of fad diets. To be fair, Atkins has been around a long time, so it has transcended the label of "fad diet." The Atkins diet involves eating very little if any carbohydrates, your diet consists only of fat and protein. That means no starchy vegetables (like beans, carrots, potatoes, corn, etc.), no bread, no pasta, almost no fruit (there are a very few fruits that are ok). The hard core Atkins diet requires the dieter to eat meat, cheese, and low-starch vegetables only. Here's the thing: the Atkins diet really does work, at least in the short term. It is the most effective diet to lose weight fast. Basically, cutting carbohydrates out of your diet lowers your overall caloric intake, and it also requires your body to start processing fat. Your brain requires carbohydrates to work, so your liver will "produce" carbohydrates from your body's stores and food for your brain's use. Your liver will also burn stored fat to make up for the calorie deficiency, hence weight loss. So, if you want to drop 10-20 pounds quick (like for a wedding, or a vacation, or seeing your ex at an event), Atkins is the way to do it. There is a catch though: it doesn't work for the long term. #1: Almost no one can stand not eating carbs forever. No cookies, no cake, no pasta, no bread, nothing! Not even most fruits! Even the most staunch dieter will crack eventually, and probably go overboard on a carb binge. It is a very one-sided diet, and those never work forever. #2: It is really hard on your liver. Your poor liver has to make sugar/carbs for your brain, and also process the fat/protein you eat, and also burn your stored fat. Long-term Atkins dieters show liver stress, which can hurt your liver function long-term. #3: You might have a fuzzy brain. Your brain requires glucose (sugar) to function, and some people on the Atkins diet report sleepiness, forgetfulness, and difficulty in focusing/paying attention. #4: It is hard to be on the Atkins diet. Your friends get sick of your diet restrictions, your family gets sick of it, and while traveling it is really hard to adhere to the diet.
So, Atkins is great for quick trim-ups, not so good for long-term weight loss!
Another diet that works almost as fast as Atkins but moderates more for the long-term is the South Beach Diet. It starts out for 2 weeks like Atkins, but then loosens up a bit.