I'm a fan of the South Beach Diet. As Lola says, it's mostly common sense. Many people on it call it a "way of eating" or a "way of life" because it's not a diet that you go on until you loose weight, it's a way of changing your eating habits to be healthier for life. What I like most about it is its individuality. There's a lot of figuring out what works for you--for example, I found out by trial and error that I can't eat any fruits or grains before 10-11am or so, otherwise I feel dizzy and sick. Until the SBD I just thought I wasn't a morning person, I didn't realize that my breakfast was making me feel bad! Now there's no way I'd ever go back to my previous way of eating, now that I know how to not feel horrid in the morning! I've heard of other people who have found out similar, but different things: like no grains past dinner time, otherwise they sleep badly, etc. Once past the initial "detox" phase (which appears to be more psychologically than physically necessary--after two weeks of no fruits, an orange tastes as sweet as chocolate and nutella--my favorite!--is so sweet it's uneatable) and the trail and error moving into the next phase, the fact that you're "on a diet" is barely visible. People might just think you're a fan of vegatables, if they notice anything.
I was actually put on it by my doctor in the states, to lower my cholesterol. That worked like a charm (240 to 190 in the first three months), and the weight loss has just been a happy bonus. Unfortunately, I've had a lot of trouble following it in the UK, having difficulty finding appropriate foods (for several months absolutely no grocery near me carried whole wheat pasta--it just reappeared last week, yeah!) and dealing with the stress of the move and new job. But I'm trying to get back on it.
As for buying the book, signing up, etc: The book isn't necessary, but reading it helps you understand how and why it works; plus it's midly entertaining. I bought it, but only read it once. There's a bunch of recipies in it, and I've made some of them, but I found that my food tastes are diametrically opposite all the book's suggestions, so it hasn't proved that useful. But if you like the foods, it's a nice recipie book. So buy it or not, but I'd suggest at least borrowing a copy so that you have an understanding of the theory behind the diet.
Don't bother with their website. It's expensive, and many people have had success on the diet without it. There's a free on-line community of SDBers at:
http://www.southbeach-diet-plan.com/forum/I've found them to be helpful--especially if you read the sticky FAQ's at the top of some forums, that have food lists that are updated as Dr Agatston revises his rules, by a few members of the community who have joined the paid site (another reason the book isn't absolutely necessary--the details of reccomended foods changes as Dr Agatston sees more about what works and doesn't and new info comes out). People there tend to be friendly, even though just about every newcomer posts the same panicked questions!
I just read the post that appeared as I typed this: I don't know anything about the Tesco GI diet, but GI is a basis behind the South Beach. The idea is too keep your blood sugar stable. It sounds like the two could be very similar. The SBD has some specific bits about heart-health too, which may make it a bit different (as it was originally a cholesterol diet not a weight loss diet--just as my doctor used it for me), but a lot of that is common sense too.
