to want to bang my head on a wall when my friend told me she intends to do The Special K Diet?

[Jaredletoisking]

My friend has always been quite big and ever since I've known her she has been doing a different diet - Weight Watchers, Slimming World and Special K.

She loses about a stone and then puts it back on.

She intended to lose a "shit load of weight" as she is being a bridesmaid for her sister in June and she announced that she's going to do The Special K Diet.

I really had to bite my tongue as I just don't feel it's my place but I just wish she'd stop doing faddy diets like Special K, where you only lose weight because you've restricted your calories and will gain the weight back if you go back to how you were eating before.

Oh dear - probably not much you can do unless she'd be willing to read about proper research into nutrition and then join the dots herself. TBH she'd probably be better off doing the Special K diet but without the special K sugaring up the milk.

It doesn't matter what she eats whether it be SK or a diet of bananas - by reducing her calorie intake she will lose weight.
I think sometimes (and I've been guilty of this) when people have an issue with their weight they need 'something' to eat that's planned and constant be it slim fast shakes or indeed a cereal - it's not so healthy but it takes out the need to plan and think about food.
It wasn't until I realised and educated myself a little about nutrition that I understood why these kind of diets don't work in the long run.

If you know she won't get upset by you discussing it why not say SK is not so healthy but porridge is much more so and more filling (imo) or ask her if she wants some help/advice.
I understand a little how you feel - there are no quick fixes in losing weight and I'd also find it difficult to watch someone you care about set themselves up to fail. Just tread carefully.