I would suggest that besides Atkins, all weight watchers and fat fighters and the like concentrate on reducing portions, reducing fat, increasing exercise and carb counting.
All of which with the right insulin regime would be productive in weight stability or reducing it.
The only addage of "no carbs after 7" which some of the places believe in is the only bit im not so sure about. if your hungey your hungry after all and starving yourself before bed if your levels arent steady is not such a great idea in my view.
If your type 1 and have the right amount of back ground insuling going on to keep you steady and then only take QA insulin to counter balance ur carb intake, i cant see how joining a weight watching club could do you any harm.
I dont think you could ever do any harm with a calorie controlled diet, exercise programme and monitoring and recording what you actually eat.
Just be aware that if you have miracle results any insulin requirement could change on the strength of weight loss.
Regards
Paul