Yes. Ketosis is a metabolic process that exists solely to get us through times of extreme famine and starvation. When you enter in ketosis, since your brain still needs glucose to survive, you're literally eating yourself from the inside to get said glucose. Ketosis suppresses thyroid, increases cortisol (since it is cortisol that breaks down your muscles and organs to get glucose) and drops your CO2 drastically, which means your mitochondria stop making a lot of energy. The "carb flu" that people get is their body being forced to find different metabolic pathways to deal with a much less efficient energy source (fat) now that they are deprived of their body's preferred fuel (glucose). It takes several weeks for a lot of people's bodies to downregulate its metabolic rate enough to work comfortably on fat in a glucose-deprived environment.
Originally Posted by wiggles92
Don't put your trust in anyone on this forum, including me. You are the key to your own success.