My sister and BIL have both down it, starting around 2 years ago. It kick started them to change their lives. Tought my BIL to start thinking about what he was shoving into his mouth, being a strict counting system it meant he could focus on counting rather than eating (if that makes sense).
He lost about 5 stone, and has changed his life – now runs, swims 2k 3 times a week, mountain boards EVERYWHERE. Now stable, eats anything, but is aware what he is eating so knows better how to control it.
Sister did it with him and lost a tone too, she ended up the smallest she’s been since she was 14 (and shes now double that age with 2 kids).
Being locked into a system worked for both of them as they had to apply a system to things (both logical people) – it also helped that their kids became WW Nazi’s and despite being 4 and 6 would tell them off for eating things that were high in ‘points’.
Saying that, counting calories on a restricted calorie diet would have had the same result I guess