ketogenic diet (KD)

Last edited 11/2018

Ketogenic diet (KD)

• 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

Reference:

• Walczyk T, Wick JY.The Ketogenic Diet: Making a Comeback.Consult Pharm. 2017 Jul 1;32(7):388-396
• Masood M, Uppaluri KR. Ketogenic Diet. StatPearls (Accessed 3/11/2018)