People will say "Oh, I've tried every diet and nothing works", meaning they've tried every fad diet and never the only thing that tends to work in the long term - calorie reduction and exercise over an extended period.
How judgemental
The problem for a lot of people is that overeating is a psychological problem - and so they tend not to succeed on diets: because diets don't address the causes of emotional eating etc.
All weightloss diets work if you can stick to them. That's just a fact.
But it's a big IF - and different diets suit different people - so it's understandable that someone would say that x diet didn't work for them.
Weightwatchers is essentially a variation on calorie counting. You need to weigh and measure and this in turn teaches portion control. Weightwatchers or calorie counting are a great way to learn nutritional information, and if you've never dieted before that's good information to have.
Slimming world follows slightly different principles, and acknowledges that not all calories do the same things to your body - it allows unlimited quantities of certain foods - depending on what else you've eaten that day. for that reason it appeals to those who don't want to be too tightly controlled and have to weigh and measure everything.
GI and low carb diets (including Atkins and dukan) work by limiting foods that are processed very quickly by your body. these foods make you feel hungry faster, and are easily converted to fat. More extreme forms of these diets will put your body into ketosis - a state where you don't feel hunger and your body is burning stored fat for fuel.
Diets like slimfast, and special K etc are essentially calorie counting, but also limit the opportunity to make bad diet choices, as two meals a day are completely controlled.
VLCDs are total food replacement diets, where you live on nutritionally complete milkshakes, soups, mealbars etc, provided by a company such as Lighter Life, Cambridge Weight Plan, etc. These require massive lifestyle changes, and do have some undesireable side effects. Therefore are generally a diet of last resort for people who have not managed to overcome their compulsive behaviours around food, and therefore found less drastic diets unsuccessful. VLCDs tend to work for this category because they give very fast results, and because they allow the dieter to 'abstain' from conventional food altogether.
