This can look different for everybody, but some popular forms of this are the 16:8 diet, where you fast for 16 hours (usually from dinnertime until a late breakfast) and eat all your food within an eight-hour span. Another is the 5:2 diet, where you eat less than 500 calories for two non-consecutive days a week and then eat normally for the rest of the week.
This article was reviewed by Jes Harvey, RD, on November 7, 2019. Harvey is a registered dietitian specializing in the ketogenic diet for children and adults. She is a certified specialist in Pediatric Nutrition and educates children with epilepsy on the ketogenic diet as an anti-seizure medication. Harvey also manages a private nutrition practice consulting adults on the ketogenic way of eating.
The ketogenic diet is calculated by a dietitian for each child. Age, weight, activity levels, culture, and food preferences all affect the meal plan. First, the energy requirements are set at 80–90% of the recommended daily amounts (RDA) for the child's age (the high-fat diet requires less energy to process than a typical high-carbohydrate diet). Highly active children or those with muscle spasticity require more food energy than this; immobile children require less. The ketogenic ratio of the diet compares the weight of fat to the combined weight of carbohydrate and protein. This is typically 4:1, but children who are younger than 18 months, older than 12 years, or who are obese may be started on a 3:1 ratio. Fat is energy-rich, with 9 kcal/g (38 kJ/g) compared to 4 kcal/g (17 kJ/g) for carbohydrate or protein, so portions on the ketogenic diet are smaller than normal. The quantity of fat in the diet can be calculated from the overall energy requirements and the chosen ketogenic ratio. Next, the protein levels are set to allow for growth and body maintenance, and are around 1 g protein for each kg of body weight. Lastly, the amount of carbohydrate is set according to what allowance is left while maintaining the chosen ratio. Any carbohydrate in medications or supplements must be subtracted from this allowance. The total daily amount of fat, protein, and carbohydrate is then evenly divided across the meals.