One reason for the problems is because, unlike most diets, this one forces the body into ketosis, burning fat instead of carbohydrates for energy.
However, I wonder if part of the problem is making a sudden change. Any pet owner can tell you that sudden dietary changes tend to cause gastric distress and other problems. In some species, a switch like that can be lethal. So while keto doesn't sound like a good approach for most people, if you have strong reasons for trying it, consider making the shift gradual rather than abrupt.