Just off the top of my head, there are several Fad Diets that spring to mind: Cabbage soup diet, Atkins diet, Paleo diet, No carbs after 3 diet, Raw food diet and the list goes on!!!!
I'm not saying that none of these diets work in terms of weight loss, its not my job to tell people what they should and shouldn't be eating, but diet and food choices have become very, very complicated over time. Each diet is competing with the next to try and get people hooked and then they figure out a way to make money from you.
People need to think of the long term choices they make, is the diet going to be suitable for your lifestyle in 6 months time? 5 years time? Can you adapt your lifestyle to continue to follow that diet long term? You need to be realistic! Yes, you may see the number on the scales drop initially and you may see a change in your body shape but can you maintain it? That's the question that needs to be addressed.
I'm a firm believer in eating a variety of foods, everything in moderation. That way if you are out for dinner or a wedding etc, you are not going to feel guilty or feel like a failure for having dessert. If you are truly worried about your weight and its time to do something about it, take it back to basics - as my mum would say "stop eating crap".
The very first thing you should do is have a look at your intake of saturated fats/oils and sugar, keep a diary of what you are eating for a few days to see exactly what you are eating and what pattern you are following. Then start to look at formulating a plan to reduce the amount of junk food. This is the number 1 step in eating healthier and losing weight (if needed).
Once you have your junk food intake reduced you can then progress to look at your serving sizes and of course adding in exercise. The biggest failure in my opinion is when people try and do all 3 of these steps at once. You are setting yourself up to fail, its often too many things to try and change at once, you need to look at it as a lifestyle change and slowly adapt your lifestyle to be able to maintain it.
Lets break it down really simple...
Step 1 - Food diary to identify what foods you are actually eating
Step 2 - Cut back on Saturated fats/oils and sugar
Step 3 - Look at cutting down portion sizes (if needed)
Step 4 - Formulate an exercise plan
Please, Please, Please give this a go before you attempt any 'fad diet' or spend a tonne of money on shakes, diet pills, diet books etc. You never know, it might actually just work ;)