OK, so on another thread you asked for the pitfalls. Here's the problems I had.
Firstly, in the beginning they called the Newcastle Diet a 600 cal diet. This was factually incorrect as it was 600 cals of shakes and 200 cals of a normal meal, salad for instance. When I did it there was very little published about the Newcastle Diet and I only had snippets of info to go with. Please don't go any lower than 800 cals.
Will you be doing the shakes or normal food? Make sure you have enough fats. My mistake was to not add, say a tablespoon of olive oil, or equivalent to a salad. I ended up stopping at 7 weeks because I was in agony with pains in my bones. Eating whipped cream fixed this better than any painkillers lol.
When I was young I used to diet by eating my favourite foods, which were mostly carbs. I neglected protein as I didn't enjoy many protein rich foods and I also cut out fat as it was high calorie. Don't neglect to have protein, it's important to keep your muscles healthy, and your muscles are what help to keep your metabolism healthy so that you don't regain the lost weight at the drop of a hat.
Drink plenty of water. I used diet coke in my younger days and this was a huge mistake as it caused/exacerbated my NAFLD, another thing that helped to mess up my metabolism.
Weigh everything you eat and log it on something like MyFitnessPal, bearing in mind that the values shown there aren't always right as it also has USA data and sometimes the American values aren't the same (as we have fibre already taken off the carb figure on food labels in UK and in USA they aren't so the Americans have to do an adjustment for that, we don't). I used MFP in conjunction with the carbs and cals book and also an old calorie counter book that I have had for years. I did this even when low carbing, because if the calorific value is wrong on MFP then chances are the carbs calculation is wrong too. Nevertheless it's a good thing to use once you have been doing it a week or so. It takes a while to get used to it. Others may have different apps that they might like to recommend.
Being kicked off the PC now as hubby is using it for work. If I think of anything else I will reply again later.