Just gonna wade on in here.
2 years ago was 16 stone, now 11 stone and need to lose another stone to be bang in the middle of the 'normal' BMI bracket (at the moment, at 5'7", I am at the upper limit of normal).
I've kept a log:
I went from 16 (size 20) > 15 stone in 1.5months
15 > 14 stone in 2 months
14 > 13 stone in 4 months
13 > 12 stone in 7 months
12 > 11 stone (size 12) in 9 months
Needless to say, taking over a year in getting to where I am from 13 stone has been a heartbreaking slog. I'm currently training hard for 6 hours a week, over 5 days a week (weekly running distance is 20+ miles over 3 running sessions, 2 gym sessions of strength training). I'm feeling mega-fit and hoping to go sub-2-hours in a half marathon in a few weeks' time. But I have a visible, stubborn layer of loose flab all over (esp. belly - exacerbated by loose skin from losing weight).
I use foodfocus.co.uk to log calorie intake (obsessively - no chance of under-estimating - I weigh everything), and always under-log exercise by 10% to allow for calorie burn innacuracies. According to their calculating system, even with 10% of days being 'treat days', I should be losing 1 pound a week.
I think I have managed to mess up my metabolism by restricting calorie intake for such a long time. As others have said - the body aims for equilibrium and if the status quo remains unchanged for long periods, your body just 'copes' with that calories in/out ratio.
I need to lose this last stone. I'm fed up of boring my friends and family by being on a diet all the time. I can't give up now, though. But I don't know what to do except carry on... getting fitter and fitter and fitter... hopefully one day I will be able to have a life outside of a sports bra again.
This ramble is basically just to show that the energy in vs. energy out equation can be invalidated by circumstances. BUT it absolutely works beautifully for about 6-8 months, I reckon.