The ketogenic diet or ‘keto diet’ is a dietary approach that has been used for decades to treat specific medical conditions, such as epilepsy and type 2 diabetes.(1,2) However, more recently the keto diet is being used as a strategy for weight loss.(3,4) WHAT IS THE KETOGENIC DIET? The keto diet is characterised by a high intake of fat, adequate protein and a very low intake of carbohydrate. (1,5) While there are variations on the ratio of macronutrients, the standard ketogenic diet contains approximately 80% fat, 15% protein and 5% carbohydrates. (6) Typically, carbohydrates are reduced to less than 50 grams a day in order to allow the body to utilise fat instead of glucose as its main source of energy. (1) HOW THE KETO DIET WORKS Normally, the body’s cells use glucose, derived from breaking down carbohydrate-rich foods, as its primary source of energy. However, by depriving the body of carbohydrates via reducing intake to less than 50g per day, the body begins to deplete its glucose stores. After three to four days of consuming all available glucose, the body is then forced into a state of ketosis - where it starts breaking down fat in the liver to produce ketones, or ketone bodies, as an alternative source of fuel for the body. (1) While the actual mechanisms by which the ketogenic diet promotes weight loss is still a source of debate, there have been several reasons put forward - these include the satiating properties of fat and protein in the diet, changes in appetite-regulating hormones, and a direct appetite suppressant action of the ketone bodies.(4,3) Despite decades of dietary guidelines promoting low-fat eating, obesity rates are on the rise.(4) As a result, researchers and clinicians are continuing to shift their attention to ketogenic diet for weight loss, especially its effectiveness, and effect on health, over the long-term. (4,3) EVIDENCE BEHIND THE KETO DIET Research shows good evidence for weight loss when patients go on a ketogenic, or very low carbohydrate diet, compared to participants on a more traditional low-fat diet.(7,8,9) For instance, the results of a randomised study of 119 overweight individuals placed on a low-carb ketogenic diet, in conjunction with nutritional supplements, for 6 months revealed that the low-carb group lost 12.9kg on average, while the low-fat group lost only 6.7kg.(9) In addition, a meta-analysis of 13 randomised controlled trials found that people on the ketogenic diet had a significantly greater reduction in weight loss compared to those who followed a low-fat diet after one year. (10) REFERENCES
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