This is an advanced diet. As the intro mentions, it was designed for someone who has done all the right things with their diet and exercise, but still has 20 pounds (or so) to go. As a result, the 45 minutes of exercise most days shouldn't be a problem for someone doing this -- they're probably already doing about that.
The restrictions are pretty severe both mentally, physically, and socially. The book hints that the drop out rate is pretty high. There are very few of the prescribed meals that would allow the dieter to eat at someone else's home, much less a restaurant. Unfortunately, the book provides no explanation for its dictates. The author is an M.D., so I guess one is expected to accept that there's some science to support the diet. Somewhere.
- The diet requires eating about every 2.5 hours. That's not even possible for someone in a retail or service job, unless they want to sneak a smoothie in the bathroom (eww). The frequent eating also means not eating many meals at standard hours, which causes social issues for typical desk workers and lots of issues for full-time parents.
- The diet requires 4 mini meals and 3-4 micro meals. The meals are so small that most Americans would call them a snack; the snacks are just a forkful of food. Most advanced dieters have figured out their eating style and, for some, the micro/mini-meal causes emotional havoc.
- The diet is very clear about what you can eat every micro and mini-meal. Some people need that, um, attention to detail. It definitely makes sure that the calorie count stays pretty low. As other reviewers have mentioned, it's likely that the publisher needed that level of detail to increase the number of pages in the book. The book is hugely repetitive, because of that detail. Every 10 pages could have easily turned into a 2 page chart.
- There's a big focus on calories and fat elimination, which ramps up the crazy quotient. Snacks are allowed up to x calories and smoothies are allowed up to y calories. Sure, that provides some flexibility. For someone who's already eliminated pre-processed crap from their diet (ahem, advanced dieters, remember?), it also means you've got to measure how all the ingredients that go into each snack, smoothie, etc, before you pack your extensive collection of micro and mini-meals for work each day. In addition, foods can't be fried, salad dressings must be fat free, and egg yolks are tossed out. That means that snacks need to contain fat to avoid psychological break downs.
On a positive, the diet allows booze and diet drinks. The diet also relies a lot on smoothies, soups, and water, which could fool a body into feeling full longer. The book also says repeatedly that people should alter the diet to their personal needs.