The keto diet can lead to short-term weight loss but is not sustainable long-term and weight is likely regained after stopping the diet. People typically lose 1-10 pounds within the first week on keto as water weight, with larger individuals losing more. The keto diet puts the body in a state of ketosis, burning fat for fuel instead of carbohydrates, when carb intake is restricted and causing ketones to be used from stored body fat.