developed in the 1920s by a faith healer to help children with epilepsy, this diet induces a state that mimics carbohydrate starvation (1)
ketogenic diet primarily consists of high-fats, moderate-proteins, and very-low-carbohydrate
dietary macronutrients are divided into approximately 55% to 60% fat, 30% to 35% protein and 5% to 10% carbohydrates
specifically, in a 2000 kcal per day diet, carbohydrates amount up to 20 to 50 g per day (2)
KD is a high-fat, low-carbohydrate diet induces ketone body production in the liver through fat metabolism
the goal is to mimic a starvation state without depriving the body of necessary calories to sustain growth and development
very high-fat diet almost eliminates carbohydrates from the patient's food selection - result is the substitution of ketone bodies as a source of energy
ketone bodies replace glucose as a primary source of energy
during ketogenesis due to low blood glucose feedback, stimulus for insulin secretion is also low, which sharply reduces the stimulus for fat and glucose storage
other hormonal changes may contribute to the increased breakdown of fats that result in fatty acids
fatty acids are metabolized to acetoacetate which is later converted to beta-hydroxybutyrate and acetone
are the basic ketone bodies that accumulate in the body as a ketogenic diet is sustained
metabolic state is referred to as "nutritional ketosis"
if the body continues to be deprived of carbohydrates, metabolism remains in the ketotic state
ketone bodies acetoacetate and -hydroxybutyrate then enter the bloodstream and are taken up by organs including the brain where they are further metabolized in mitochondria to generate energy for cells within the nervous system
ketone body acetone, produced by spontaneous decarboxylation of acetoacetate, is rapidly eliminated through the lungs and urine
nutritional ketosis state is considered quite safe, as ketone bodies are produced in small concentrations without any alterations in blood pH
greatly differs from ketoacidosis, a life-threatening condition where ketone bodies are produced in extremely larger concentrations, altering blood ph to acidotic a state
classic KD is typically composed of a macronutrient ratio of 4:1 (4 g of fat to every 1 g of protein plus carbohydrates combined) - so shifting the predominant caloric source from carbohydrate to fat
lower ratios of 3:1, 2:1, or 1:1 (referred to as a modified ketogenic diet)
can be used depending on age, individual tolerability, level of ketosis and protein requirements
more 'relaxed' variants have been developed, including the modified Atkins diet (MAD), the low glycemic index treatment (LGIT) and the ketogenic diet combined with medium chain triglyceride oil (MCT)
MAD
typically net 10-20 g/day carbohydrate limit
roughly equivalent to a ratio of 1-2:1 of fat to protein plus carbohydrates
LGIT
40-60 g daily of carbohydrates with the selection of foods with glycemic indices <50
approximately 60% of dietary energy derived from fat and 20-30% from protein
MCT variant KD
uses medium-chain fatty acids provided in coconut and/or palm kernel oil as a diet supplement and allows for greater carbohydrate and protein intake than even a lower-ratio classic KD, which can improve compliance
adverse effects:
short-term effects (up to 2 years) of the ketogenic diet are well reported and established - however, the long-term health implications are not well known due to limited literature
most common and relatively minor short-term side effects of ketogenic diet include a collection of symptoms like nausea, vomiting, headache, fatigue, dizziness, insomnia, difficulty in exercise tolerance, and constipation, sometimes referred to as keto flu
symptoms resolve in a few days to few weeks (2)
adequate fluid and electrolyte intake can alleviate some of these symptoms
long-term adverse effects include:
hepatic steatosis, hypoproteinemia, kidney stones, and vitamin and mineral deficiencies
cautions and contraindications
with respect to diabetic patients
appropriate adjustment of insulin or oral hypoglycemic agents is required to avoid severe hypoglycaemia if the medications are not appropriately adjusted before initiating this diet
ketogenic diet is contraindicated in patients with pancreatitis, liver failure, disorders of fat metabolism, porphyrias, primary carnitine deficiency, carnitine palmitoyltransferase deficiency, carnitine translocase deficiency, or pyruvate kinase deficiency
false positive breath alcohol test
if on a KD then this can rarely cause a false positive breath alcohol test
secondary to ketonemia, acetone in the body can sometimes be reduced to isopropanol by hepatic alcohol dehydrogenase which can give a false positive alcohol breath test result
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