Being in a metabolic state of ketosis can have both positive and negative effects. Because ketones provide more energy than glucose, ketones are a superior fuel source for the brain. Common effects include improved mental clarity, focus, cognitive functioning, energy levels, sleep, mood, and overall sense of wellbeing.
On the opposite spectrum, some individuals experience the keto flu when starting the ketogenic diet. The keto flu causes flu-like symptoms including headaches, fatigue, nausea, and muscle cramps. These symptoms are caused by dehydration and can be combated by supplement (or consuming) plenty of electrolytes and drinking plenty of water.