I've taken on a pretty strict keto diet and experienced none of the typical affects. No insane hunger, no lethargy, tiredness, minimal weight gain.
Ive taken it while not on any kind of diet and could not eat enough, I was constantly hungry, slept like a rock, I had pretty brutal lethargy, I had to really force myself to get up and do anything...but once I finally did get started I could get a decent workout in after I got moving. But the initial effort to get up and get anything done was pretty tough.
It was a lot more manageable if I split the dose in 2. And took it mid afternoon and just before bed.
While in ketosis I noticed nothing.