I had it on day one and two, didnt feel hungry, just sick ugh... I switched to tetras and it went. I read that the nausea could be due to vitamin concentration and I split the packs that made it worse cause I was sick more often.
I also read that some people that are lactose intolerant find the shakes make them nausous. Personally I am not lactose intolerant or at least I never had a problem with milk of any kind. But the soups and tetras I can take without feeling like that.