For the home dieter it might be overly strict.
However, I consider this to be "medically supervised" so the diet and exercise can be more rigorous than you would do yourself at home.
It is like the Rice Diet Clinic here in NC. If you read the book to do it at home there is the basic diet that you do one day out of the week and the rest of the week is more relaxed in calorie restriction. When you do it in house you do that very basic diet for as many days in a row that you can because they are checked by the medical staff and if you are being monitored regularly you can go with a stricter version of the diet.
When you are talking very heavy people if you get them of sugar and salt they can lose 10 pounds of water in a week even if they don't lose any real weight (meaning that if they had a meal or two the way they usually eat they'd gain all 10 pounds back in no time at all)
Imaginary friends by Bob!