How do you lose 3lb a week?

[somanybabyseagulls]

Browsed several of these threads and a lot of people seem to lose a fair bit each week, just wondering how it's done?

3lb a week is a bit drastic - temds to be mostly water at first.
We eat no starchy carbs after 5pm (bread potatoes, pasta, rice) and don't eat junk during the day. I;ve lost 19lb since mid-Jan