The idea here is to make your body go into ketosis quickly and this will only happen with an empty stomach and a low - intensity activity like walking for a few minutes. (wisejug.com)
But I have been fat - adapted for quite a while, go into ketosis quickly. (idmprogram.com)
I think it is ok to go into ketosis for short periods of time but it is an aggressive approach to weight loss. (fitnesscontrarian.com)