Any diet that reduces carbs to absolutely minimal levels will cause ketosis as you change your metabolism to burn fat instead of carbs... Take a look at the sticky in this forum which explains all about what ketosis is.... http://www.minimins.com/cambridge-diet-forum/18542-ketosis.html (post number 3)
The problem I found with Atkins <which also puts you in ketosis>, is that i was not getting enough nourishment.. thats the good thing about SS I think!