I've known quite a few people that have gone on the atkins diet, most lead very active lives as well. Basically, (as I understand it, my fiance' knows more about it than I do so I just listen to her) you have a 2 week induction period where you can have no more than 20 grams of Carbs per day. This means cutting out grains, fruit, milk etc. There's a big list online somewhere of what you can eat, really it's quite a bit. After the 2 weeks you can start to introduce some more carbs and foods back in. I haven't hit the 2 week mark yet though. It is hard giving up potato's and french fries and garlic bread etc, but I've been doing well with it.
The first day was hell, I felt dizzy, tired, pretty dazed. They call that the induction flu, typically it lasts one to two days. This is because your body goes into shock almost since it's not getting carbs. The good news is, when that goes away I started feeling better than usual. Your body starts to burn it's own fat to get the carbs it needs. Thats why the weight loss is so dramatic in the first couple of weeks. Once you start to introduce more carbs back in, you're body has trained itself to continue burning fat for more carbs.
Honestly, it's not that hard, and I have more energy than I used to. I just miss some of the foods, had a "protien burger" today. All the stuff in a normal hamburger, but wrapped in lettuce instead of a bun, weird. And a ceasar salad with no croutons instead of fries. It helps that I love vegetables and salads, but there's even atkins chocolate bars and peanut butter cups for those chocolate cravings. Kind of expensive, but it's not a forever thing.
As for the pencils, they were a good source of fiber but they didn't feel great coming back out