Is there really a favorite celebrity diet? Certainly, some diets consist of cigarettes and water and not much else. There is also the jacked-up-on-caffeine diet, which makes them so jittery and jumpy they can't possibly eat.

Seriously, though, there are actual diets that the celebs follow and with great success.

The most popular diet lately is the one that modifies carbohydrate intake. There are a few different variations on this theme, such as the Zone Diet, the Atkins Diet, the Mediterranean Diet and the South Beach Diet. Basically, it emphasizes protein intake and limits starchy foods and sugars. Jessica Alba keeps her great form by following this diet, as does Jennifer Aniston and Demi Moore. Of course, Demi has likely had help by some other means as well, but we know that Jennifer Aniston has had no work done on her body and is a religious follower of the Zone diet.

The Zone Diet, pioneered by Dr. Barry Sears, promises moderation and flexibility. It's not as rigid as the high-protein Atkins Diet, and claims to work by controlling insulin and reducing inflammation within the fat cells. When these fat cells become inflamed, that's when we purportedly see the weight gain. Apparently, by regulating the insulin and the hormonal balance, you can control your hunger and accordingly your weight gain. Hey - not only does it work for Jennifer, Demi and Jessica, but Brad Pitt and Cindy Crawford are believers, too. They all look pretty good to me, so something must be working!

Another popular diet is the Atkins Diet, which is similar to the Zone but more extreme. If you look at its followers, this makes sense. Super-skinny stars like Renee Zellwegger, Sarah Jessica Parker and Calista Flockhart are all big fans!

The Atkins Diet was made famous by Dr. Robert Atkins, and has four stages to it, all of which are very low-carbohydrate. The first stage of the program only allows for consumption of 20 net carbs a day! This is very difficult to follow, and you must be extremely focused and dedicated to the weight loss to get through the first two weeks of this program. Even after the first two weeks, Atkins followers are only allowed to increase their carbohydrate intake by about 5 grams per day. By the end of the program, this number increases slightly, but never by a lot. Arguments against this diet are that it is far too hard to maintain in a 'real' person's life. Sure, if you have the money for a personal chef as well as an assistant who can follow you around with your special food, this will work for you - so long as you have the discipline - as it has for the celebrities listed above as well as Minnie Driver and Geri Halliwell of the Spice Girls.

Of course, there are still the oldies-but-goodies such as Weight Watchers and Jenny Craig. We all have seen the crazy amount of weight Kirstie Allie has lost on the Jenny Craig program, and now she is joined by Valerie Bertinelli as another spokeswoman. Their method is portion control, for the most part. Jenny Craig is slightly newer than Weight Watchers, but very successful and similar in nature.

Just look at how much weight Jenny McCarthy has lost following the Weight Watchers program! She gave birth to her baby and needed to lose the pregnancy weight she had gained. Sarah Ferguson (the Duchess) was their most famous spokesperson until Jenny. But the great thing about Weight Watchers is that it is readily available for all of us common folks, from the stores and clinics where you weigh in to the many entrees and desserts available in the frozen section of your nearest grocery store. People are assigned points to each food, and given your current weight and how much you want to lose; you are allowed a certain number of points per day. This makes it very easy to follow!

All of these diets sound completely reasonable, right? Well, we can't stop there. There are also the freakish diets of the stars that nobody should try. Did you really expect the celebs to only follow the reasonable, medically-advisable diets?

Janet Jackson, for example, is only now re-introducing whole foods back into her diet. She has basically subsisted on liquid meals prepared by her nutritionist until recently. Demi Moore drinks a lot of herbal tea to ward off cravings for actual food, and thinks this is made healthier by taking vitamins with that tea. No wonder she stays so slim! Pop star Fergie downs tablespoons of apple cider vinegar. Hey, nobody said these stars look the way they do easily.