So caffeine and the stimulant in chocolate raises insulin. Insulin shuts down fat oxidation. So, if you are in ketosis, on VLC, won't drinking coffee or eating raw dark chocolate shut of that nice fat burning mode? I know when I am VLC, if I have ANY, I mean a few SIPS of tea or nibbles of cacao, I IMMEDIATELY get that "hormonally hungry" feeling.
So I've found that on meat/fat only days, in Ketosis, caffeine or stimulants of any kind make me feel terrible, and VERY hormonally hungry between meals (with the same timing and calories that on non-caffeine days are satiating). I literally can scarcely make it to my next meal, feeling utterly starved and losing all concentration.
However, on carb-up days after exercise, I can eat some chocolate or drink some tea, and while I feel quite stimulated (perhaps too much, I seem to be sensitive), it isn't a bad feeling, and I don't get the hunger afterwards.