Not diet in terms of losing weight but rather more healthy eating (which will actually lead to weight loss anyway). For years I've accepted the government supported recommendations on the food pyramid, saturated fats, fibre, 5 a day, cholesterol etc. and laughed at the various 'fad' diets such as Atkins, South Sea, Dukan, Mediterranean etc.
This year I've become more interested in some of the alternatives as I've seen the seesaw effect of official recommendations. I think eggs were the first issue, where they first recommended only a couple a week and had people eating egg white omelets then decided that eggs had 'good' cholesterol but still told you to limit consumption to 1-2 a day for no obvious reason. Oils were the next where butter is condemned and margarines have been pushed on us, except they originally used hydrogenation to make the oils solid and the trans fats proved to be very unhealthy. They now have another process which is looking even riskier long term.
It dawned on me that a lot of the fad diets were simply low carb diets and if you strip away all the stupid quirks which let them sell a book as a unique diet they are basically the same. The site I prefer is Primal Blueprint 101 | Mark's Daily Apple but there are a lot of other sites backing him up.
You can find all sorts of weird ideas supported on the internet of course, so you might want to stick to what your government advise, the UK have consulted with experts in nutrition to help formulate their latest policies see McDonald's and PepsiCo to help write UK health policy | Politics | The Guardian
You should be aware that most diet related research is sponsored by big multinationals (ie. Kellogs, McDonalds, PepsiCo) and that many scientific papers are written by the research departments of multinationals and given to eminent academics to put their name to it. They are paid fees as consultants etc. but in reality they just proof read the research and put their name to it.