Stay hydrated. As carb intake is lowered, the kidneys will start dumping excess water being retained as a result of the former higher carb intake. Make sure to drink enough water to replace what gets lost. The old 6-8 glasses is a good rule, I guess, although just drinking to thirst will probably do the trick. If you find yourself getting headaches and muscle cramps, you need more water, and more minerals such as salt, magnesium and potassium, because the water loss also takes minerals with it. (See my low carb diet side effects page for more info).
What we do know, based on carefully conducted laboratory testing of overweight men, is that going keto probably doesn't help burn more body fat than a regular regimen. Instead, it forces people to dramatically curb their sugar intake (remember, sugar is 100% carbohydrate) and kick processed foods to the curb. Those are both good habits for overall health and blood-sugar levels, and they can help reduce your likelihood of developing cancer.
Our bodies are incredibly adaptive to what you put into it – when you overload it with fats and take away carbohydrates, it will begin to burn ketones as the primary energy source. Optimal ketone levels offer many health, weight loss, physical and mental performance benefits.1There are scientifically-backed studies that show the advantage of a low-carb, ketogenic diet over a low-fat diet. One meta-analysis of low-carbohydrate diets showed a large advantage in weight loss. The New England Journal of Medicine study resulted in almost double the weight loss in a long-term study on ketone inducing diets.