Some cultures and religions have restrictions concerning what foods are acceptable in their diet. For example, only Kosher foods are permitted by Judaism, and Halal foods by Islam. Although Buddhists are generally vegetarians, the practice varies and meat-eating may be permitted depending on the sects.[2] In Hinduism, vegetarianism is the ideal. Jains are strictly vegetarian and consumption of roots is not permitted.
On the ketogenic diet, carbohydrates are restricted and so cannot provide for all the metabolic needs of the body. Instead, fatty acids are used as the major source of fuel. These are used through fatty-acid oxidation in the cell's mitochondria (the energy-producing parts of the cell). Humans can convert some amino acids into glucose by a process called gluconeogenesis, but cannot do this by using fatty acids.[57] Since amino acids are needed to make proteins, which are essential for growth and repair of body tissues, these cannot be used only to produce glucose. This could pose a problem for the brain, since it is normally fuelled solely by glucose, and most fatty acids do not cross the blood–brain barrier. However, the liver can use long-chain fatty acids to synthesise the three ketone bodies β-hydroxybutyrate, acetoacetate and acetone. These ketone bodies enter the brain and partially substitute for blood glucose as a source of energy.[56]
The ketogenic diet is not a benign, holistic, or natural treatment for epilepsy; as with any serious medical therapy, complications may result.[28] These are generally less severe and less frequent than with anticonvulsant medication or surgery.[28] Common but easily treatable short-term side effects include constipation, low-grade acidosis, and hypoglycaemia if an initial fast is undertaken. Raised levels of lipids in the blood affect up to 60% of children[38] and cholesterol levels may increase by around 30%.[28] This can be treated by changes to the fat content of the diet, such as from saturated fats towards polyunsaturated fats, and if persistent, by lowering the ketogenic ratio.[38] Supplements are necessary to counter the dietary deficiency of many micronutrients.[18]
After about two to seven days of following the keto diet, you go into something called ketosis, or the state your body enters when it doesn't have enough carbs for your cells to use for energy. That's when you start making ketones, or organic compounds that your bod then uses in place of those missing carbs. At this point, your body also starts burning fat for more energy, says Beth Warren, R.D., founder of Beth Warren Nutrition and author of Living A Real Life With Real Food.

The ketone bodies are possibly anticonvulsant; in animal models, acetoacetate and acetone protect against seizures. The ketogenic diet results in adaptive changes to brain energy metabolism that increase the energy reserves; ketone bodies are a more efficient fuel than glucose, and the number of mitochondria is increased. This may help the neurons to remain stable in the face of increased energy demand during a seizure, and may confer a neuroprotective effect.[56]
For patients who benefit, half achieve a seizure reduction within five days (if the diet starts with an initial fast of one to two days), three-quarters achieve a reduction within two weeks, and 90% achieve a reduction within 23 days. If the diet does not begin with a fast, the time for half of the patients to achieve an improvement is longer (two weeks), but the long-term seizure reduction rates are unaffected.[44] Parents are encouraged to persist with the diet for at least three months before any final consideration is made regarding efficacy.[9]

After initiation, the child regularly visits the hospital outpatient clinic where they are seen by the dietitian and neurologist, and various tests and examinations are performed. These are held every three months for the first year and then every six months thereafter. Infants under one year old are seen more frequently, with the initial visit held after just two to four weeks.[9] A period of minor adjustments is necessary to ensure consistent ketosis is maintained and to better adapt the meal plans to the patient. This fine-tuning is typically done over the telephone with the hospital dietitian[19] and includes changing the number of calories, altering the ketogenic ratio, or adding some MCT or coconut oils to a classic diet.[18] Urinary ketone levels are checked daily to detect whether ketosis has been achieved and to confirm that the patient is following the diet, though the level of ketones does not correlate with an anticonvulsant effect.[19] This is performed using ketone test strips containing nitroprusside, which change colour from buff-pink to maroon in the presence of acetoacetate (one of the three ketone bodies).[45]


The original therapeutic diet for paediatric epilepsy provides just enough protein for body growth and repair, and sufficient calories[Note 1] to maintain the correct weight for age and height. The classic therapeutic ketogenic diet was developed for treatment of paediatric epilepsy in the 1920s and was widely used into the next decade, but its popularity waned with the introduction of effective anticonvulsant medications. This classic ketogenic diet contains a 4:1 ratio by weight of fat to combined protein and carbohydrate. This is achieved by excluding high-carbohydrate foods such as starchy fruits and vegetables, bread, pasta, grains, and sugar, while increasing the consumption of foods high in fat such as nuts, cream, and butter.[1] Most dietary fat is made of molecules called long-chain triglycerides (LCTs). However, medium-chain triglycerides (MCTs)—made from fatty acids with shorter carbon chains than LCTs—are more ketogenic. A variant of the classic diet known as the MCT ketogenic diet uses a form of coconut oil, which is rich in MCTs, to provide around half the calories. As less overall fat is needed in this variant of the diet, a greater proportion of carbohydrate and protein can be consumed, allowing a greater variety of food choices.[4][5]
People use a ketogenic diet most often to lose weight, but it can help manage certain medical conditions, like epilepsy, too. It also may help people with heart disease, certain brain diseases, and even acne, but there needs to be more research in those areas. Talk with your doctor first to find out if it’s safe for you to try a ketogenic diet, especially if you have type 1 diabetes.
It all depends on you. Researchers suspect that the 16:8 diet isn’t quite as effective for weight loss as more extreme forms of fasting, like alternate-day fasting. On the other hand, studies suggest that alternate-day fasting doesn't produce better weight loss results compared to daily calorie restriction. Plus, eating only every other day is very restrictive and can be tougher to stick to.
Lots of apps and websites offer keto diet challenges—basically, a blueprint for the keto diet with a fixed starting and ending point (they typically last for a week to a month, though some may be longer). Speaking of apps, plenty of keto-centric ones are right at your fingertips (a.k.a., your smartphone), like the KetoDiet app, which can help you calculate your macros and track your keto diet effectively.
Lose It! This two-week phase is designed to jump-start your weight loss, so you may lose up to 6 to 10 pounds (2.7 to 4.5 kilograms) in a safe and healthy way. In this phase, you focus on lifestyle habits that are associated with weight. You learn how to add five healthy habits, break five unhealthy habits and adopt another five bonus healthy habits. This phase can help you see some quick results — a psychological boost — and start practicing important habits that you'll carry into the next phase of the diet.
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