The ketogenic diet is based on a low carbohydrate intake and a higher fat intake. Various definitions exist. The most commonly used is as follows:^[1][2][3]

• Less than 50 grams of carbohydrates per day
• a minimum of 45% (and up to a maximum of 80%) of calories from fat
• 45% of calories from fat
• Remaining calories from protein

A VLCKD is more frequently used by physicians for treating people with obesity or epilepsy. It is defined as follows:^[4]

• Less than 800 calories per day
• Less than 30 grams of carbohydrates per day
• Around 45% of calories from fat
• Around 40% of calories from protein