Doesn't always work. I'm a UK size 12/14 and 159cm tall. I used to have bmi of 48, and it's now 30 (was as low as 28).
I've been eating between 1200-1300 cals a day, yet I cannot lose weight unless I keep to 1000 cals/day.
Originally, I saw a dietician for about a year to help me lose the weight and she told me that I'd messed my metabolism up so much by all the years of dangerous/fad diets I'd done that I'd never be able to eat normally and would have to keep to about 1000cals/day to maintain my weight (this was about 7 years ago).
She's not wrong either because over the last few years of eating around 1200-1300 cals/day I've gained about 2 stone.
I've just started losing it again over the last 5 months, but it's very slow (about 1kg/ month), and I'm having to stick to 1000cals/day, despite my TDEE being 1677 and my BMR being 1398. Even the lowest TDEE I've found still says I need 1541cals with BMR of 1401cals to maintain my weight.
Tbf, though, one diet I tried resulted in me needing emergency surgery to fix the problems it caused.