You can't really tell them apart. On the SCD diet it's called "bacterial die-off", in the candida/GAPS circles it's called "candida die-off", in the Paleo circles it's called "carb flu", and in the keto circles it's called "keto flu". In reality, it's the same thing, a mix of both bad organisms die due to less sugar food for them, and going through sugar withdrawal yourself. Toxins are released, and everyone starts feeling bad. But you survive, they don't.