Low-calorie diets usually produce an energy deficit of 500–1,000 calories per day, which can result in a 0.5 to 1 kilogram (1.1 to 2.2 pounds) weight loss per week. One of the most commonly used low-calorie diets is Weight Watchers. The National Institutes of Health reviewed 34 randomized controlled trials to determine the effectiveness of low-calorie diets. They found that these diets lowered total body mass by 8% in the short term, over 3–12 months. Women doing low-calorie diets should have at least 1,000 calories per day and men should have approximately 1,200 calories per day. These caloric intake values vary depending on additional factors, such as age and weight.
The ketogenic diet is indicated as an adjunctive (additional) treatment in children and young people with drug-resistant epilepsy. It is approved by national clinical guidelines in Scotland, England and Wales and reimbursed by nearly all US insurance companies. Children with a focal lesion (a single point of brain abnormality causing the epilepsy) who would make suitable candidates for surgery are more likely to become seizure-free with surgery than with the ketogenic diet. About a third of epilepsy centres that offer the ketogenic diet also offer a dietary therapy to adults. Some clinicians consider the two less restrictive dietary variants—the low glycaemic index treatment and the modified Atkins diet—to be more appropriate for adolescents and adults. A liquid form of the ketogenic diet is particularly easy to prepare for, and well tolerated by, infants on formula and children who are tube-fed.