Popular Dietary Models - Ketogenic Diet

Question 1

Ketogenic Diet

Answer 1

First introduced as a treatment for epilepsy in the 1920s.
* Research shows benefits in a range of health issues.
* Macronutrient ratio is: 75% fat, 20% protein, only 5% carbs.
* The significant reduction in carbs changes the body’s primary fuel source from glucose to fat, putting the body into ketosis.
* When glycogen stores are depleted, glucose levels become insufficient to support normal fat oxidation.
ketosis = a metabolic state characterised by raised levels of ketone bodies in the body tissues.

Question 2

Ketones and Ketosis

Answer 2

Fat is converted to ketones in the liver and ketones are transported to body tissues, to enter the mitochondria for generation of ATP.
* Ketone bodies (ketones) are able to cross the blood-brain barrier to provide an alternate source of energy for the brain.
* Note that ketosis —a normal physiologic response is distinct from keto-acidosis where ketone bodies exceed levels the body can deal with leading to a decrease in pH —seen with poorly-controlled diabetes.

Question 3

Foods to eat:

Answer 3

• Meat: Red meat, steak, ham, sausage, bacon, chicken, turkey.
• Fatty fish: Salmon, trout, tuna, mackerel.
• Eggs, butter, cheese, creams.
• Nuts and seeds: Almonds, walnuts, flax seeds etc.
• Oils, avocados
• Low-carb veggies: Most green veggies, tomatoes, peppers, etc.

Question 4

Foods to avoid:

Answer 4

• Foods made with flour: Such as bread and pasta.
• Grains: Rice, oats, and quinoa.
• Foods with lots of sugar: Honey, syrup, fruits.
• Starchy vegetables: Potatoes, corn and peas
• Lactose-rich dairy products: Milk, ice cream, yoghurts

Question 5

Benefits:
Epilepsy

Answer 5

Epilepsy:
* Significant reductions in seizure number (30–40%) observed in clinical trials.
o It thought that ketone bodies exert anticonvulsant effects and decrease neuronal excitability.

Question 6

Benefits:
Neurological Disease

Answer 6

Neurological disease: e.g. Alzheimer’s and Parkinson’s disease.
* A neuroprotective effect by ketone bodies is proposed relating to:
o Increased ATP production and reduced ROS in nervous tissue.
o Increased synthesis of PUFAs —helps stabilise cell membranes.
o An influence on neurotransmitter activity in neurons.
ROS= Reactive Oxygen Species

Question 7

Benefits:
Cancer

Answer 7

Cancer:
* Thought to change the preferred energy source of some cancer cells, e.g. those expressing insulin and IGF-1 receptors.
* Research has mostly focused on brain tumours.

Question 8

Benefits:
Cardiovascular Disease

Answer 8

Cardiovascular disease:
* Marked improvements in triglyceride levels.
* Increased HDL cholesterol and increased LDL cholesterol size, which have lower atherogenic potential

Question 9

Benefits:
Type II Diabetes

Answer 9

Type II Diabetes:
* Shown to improve glycaemic control and insulin sensitivity.

Question 10

Benefits:
Weight Loss

Answer 10

Weight-loss: The ketogenic diet is associated with long-term weight management. Proposed mechanisms include:
* Lack of glucose in the diet leads to a decrease in insulin, in turn reducing lipogenesis and increasing lipolysis.
* Appetite-suppressant effect of ketosis related to modification of levels of hormones that influence appetite —ghrelin and leptin.
* Increased metabolic cost of gluconeogenesis and the thermic effect of protein.
lipogenesis: Synthesis of fatty acids
lipolysis: Breakdown of fats
gluconeogenesis: Generation of glucose from a variety of sources

Question 11

Disadvantages:

Answer 11

• Tachycardia, dehydration, acidosis, hypoglycaemia and constipation (lack of fibre), kidney stones, overacidity, arthritis.
• Key vitamin and mineral deficiencies: Lack of plant-based polyphenols and phytonutrients may require supplementation.
• Dyslipidaemia and elevated cholesterol levels: High fat intake.
• The quality of dietary fats needs to be considered.
• Long-term viability and limitations of following a restrictive diet such as keto needs to be assessed by the practitioner. Long-term compliance can be difficult.