The ketogenic diet; also known as the keto diet, has gained in popularity over the past few years for its claims surrounding weight loss. It involves having a high fat and protein diet, whilst restricting the amount of carbohydrates (1). The keto diet it is often termed a ‘low-carb’ diet, which refers to eating less than 50g of carbohydrates per day, sometimes even as little as 20g (2). For reference, it is recommended to obtain 50% of total dietary energy from carbohydrates, which for an average person this can range between 200-250g of carbohydrates per day (3).
The restriction of carbohydrates is replaced with fat and protein, therefore foods included on the keto diet are:
• Butter & oils
• Cheese, cream, mayonnaise
• Meat, fish & eggs
• Avocado & nuts
• Low carbohydrate vegetables (kale, broccoli, onions)
Foods that are discouraged include:
• Breads, grains & pasta
• Beans & pulses
• Fruit & sugary drinks
• Higher carbohydrate vegetables (potatoes, carrots)
The keto Diet is not new; low-carbohydrate diets have been coming in and out of fashion, including the Atkins diet which was popular back in the 1970s (1). But it first materialised as a treatment for childhood epilepsy in the 1920s (4) which involved fasting, a precursor to the keto diet. It was then decided to use the ketogenic diet for sustainability as opposed to fasting (5).
How does the keto diet ‘work’?
Carbohydrates are the body and brain’s preferred source of energy and when this is reduced considerably, the body needs to find another fuel source. It does this by using up energy stores within muscles and the liver. It breaks down fat and creates carbohydrates for itself through the process called gluconeogenesis (6).
By not having enough energy regularly coming from carbohydrates (estimated threshold is below 65-180g/day), reserves of glycogen stores can become depleted. Consequently, glucose oxidation decreases and fat break down increases (ketogenesis) (6). During ketogenesis the body produces something called ketone bodies within the liver in order to be used as energy. Some of the ketone bodies enter cells to be utilised, however the rest are lost via urine, the skin and breath without being used (6).
The keto diet is unusual as it stimulates fasting pathways, despite being a high energy state (4). Following the keto diet does not mean you are in Ketosis or producing ketone bodies necessarily. It is hard to keep the body in this state and by simply eating a food or drink that is rich in carbohydrates for most people, would take you out of ketosis.
Following the keto diet is very restrictive and can lead to nutrient deficiencies (1) and possible health risks (constipation and kidney problems), not to mention the physical and mental stress it can cause on the body (7), along with the possibility of instigating obsessive eating patterns. Our body is extremely clever at adapting to situations in order to survive, but the risk is that the body will start to burn proteins (i.e. your muscle) for energy, resulting in the person having less energy and feeling fatigued.
There are medical cases (Type 2 Diabetes) where the keto diet may be used to help control blood sugar levels but should only be used under medical supervision or in a clinical trial (4). There is debate whether low-carbohydrate diets and the role of ketosis is primarily due to the process of ketosis or simply due to the voluntary calorific restriction (6). More research is certainly needed.
The keto diet is recommended to be only used when under professional supervision, where it can be effective. However, for the general public, it is a very restrictive diet where it excludes a macronutrient that has an array of benefits from wholegrains, beans, vegetables that contain a variety of micronutrients and not to mention fibre. A well-balanced diet involves diversity, not excluding certain food groups.
This blog post was written by Anna Hood who is a second year Nutrition student at St Mary’s University. Anna has aspirations to go into 1-1 client work, incorporating fitness and nutrition together (sports nutrition and weight management). Anna is passionate about a non-diet approach and recently interned for Faye Townsend. Additionally she works as a recipe developer and loves to cook and making food appetising. You can find out more about Anna on her Instagram @a__nourish.
(1) Giroux, N.F. (2020). The keto diet and Long-term weight loss: is it an option? Inquiries Journal. http://www.inquiriesjournal.com/articles/1807/the-keto-diet-and-long-term-weight-loss-is-it-a-safe-option
(2) Examine.com. (2017). “Does “low-carb” have an official definition?.” https://examine.com/nutrition/does-low-carb-have-an-official-definition/
(3) SACN. (2015). “Carbohydrates and Health” https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/445503/SACN_Carbohydrates_and_Health.pdf
(4) Newman, J.C & Verdin, E. (2014). ketone bodies as signalling metabolites https://reader.elsevier.com/reader/sd/pii/S1043276013001562?token=835F20C91CDCE374F171505BB3BFA3F82ED735E444E298094E23040A593EFA1B20E9591907CED0C5E319EEFFD3C06F77
(5) Wheless, J.W. (2008). History of the ketogenic diet.https://onlinelibrary.wiley.com/doi/full/10.1111/j.1528-1167.2008.01821.x
(6) Pogozelski et al. (2006). “The metabolic effects of low‐carbohydrate diets and incorporation into a biochemistry course” https://iubmb.onlinelibrary.wiley.com/doi/full/10.1002/bmb.2005.494033022445
(7) Paoli. (2014). “Ketogenic Diet for Obesity: Friend or Foe?” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3945587/
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