I have been doing Weight Watchers since early March, and have lost just under 2lb, on average, per week. So that would be half a stone in a month.
It can make you a bit obsessive, as you have to track everything you eat, but its quite good for enabling you to think about what you are
eating, and what you could swap for those unhealthy snacks you reach for without thinking. (So, in the mid afternoon, instead of crisps or a biscuit, some crunchy pickled vegetables or a banana.)
It's quite simple to follow, and basically, if you eat a load of lean meat and vegetables, you can eat loads, but you can also factor in things like cheese, ans sugary or starchy things, so long as you don't eat too much of them. So you don't really have to give up any foods, entirely.
I have just been using the app, not attending meetings. You do have to pay for it, and obviously you could do similar without the subscription, but I find having the app makes me stick to it better than just knowing what I should be doing. (Which, frankly, we all do, really.)