Ok my thoughts on sustaining weight-loss in the long-term based on quick google research/gut feelings...I'm fairly new to researching all this so bear with me pleaSE. This was just a v quick search of academic-type articles - not checked whether fully peer-reviewed etc etc so stand to be corrected...
Anyway, apparently to sustain weight-loss long-term requires you to maintain, for example, a 20% calorie reduction to sustain a 10% weight-loss (due to body's evolutionary propency to store fat in times of perceived "need" ie you cut, it'll want to store more...)
Obviously this does depend on how much energy you expend. One study found that women exercising an additional 5 hours a week managed to maintain their weight loss long-term, but this is additional so how realistic is it to maintain the target level of weight-loss in the long-term??
Maybe if we set a target to aim for we then need to allow for slippage in the long-term. So, if we want to lose a stone, we need to accept that even with a diet such as ID we're likely to maintain 1/2 stone loss rather than the full stone..Maybe accepting this is key to avoiding the yo-yo dieting scenario which is so exploited by the dieting industry?
Also re exercising, as musle obviously weighs more than fat,it is not a clear cut picture to focus solely on wieght loss. should we rather focus on inches lost, dropping dress sizes etc? What are you using?
Apologies for stating the blooming obvious.. Food for thought, excuse the pun..