What the health: Ketogenic diet - fix or fad?

27 Feb 2019

Ketogenic diet - fix or fad?Is this diet a fad? No, the ketogenic diet in itself is not a fad, but the reason why it is practiced, and how it is practiced may be!

Foods are made of macronutrients (protein, carbohydrate and fat), micronutrients (vitamins and minerals), and a variety of other health promoting constituents (fibre, phytonutrients). Macronutrients are building blocks for the body’s structures and optimal function. They also yield energy that the body uses to produce its fuel.

The healthy eating recommendations for the proportion of carbohydrate, fat and protein in the diet are 45 to 65 per cent, 20 to 35 per cent, and 15 to 25 per cent of total daily energy intake respectively. These recommendations are addressed to the healthy general population, and aim to ensure the provision of micronutrients and other constituents as well as energy requirements through foods alone (as opposed to supplementation). Indeed, foods that contain the macronutrients also contain a variety of micronutrients required to avoid deficiencies. But is this ratio of macronutrients the only way to eat healthily? Not necessarily.

Macronutrient “manipulation”, or changing the ratio of macronutrients in the diet, can be practiced for optimising individual dietary needs. New understandings of genetic individuality in terms of metabolism suggest that dietary plans with varying ratio of macronutrients may be indicated to achieve individual optimal health outcomes.

The ketogenic diet is by definition a diet that promotes the production of ketone bodies (KB). KB are molecules produced in the liver as a result of using fat (dietary or from body stores) as primary source of energy. KB are then released into the circulation, and delivered to muscles, the heart and the brain where they can also be converted to fuel to meet energy demands. In the last three years, research in the field of metabolism and healthy ageing has revealed the health benefits of KB beyond providing energy. KB are shown to promote anti-inflammatory, anti-antioxidant, and autophagy (cell “spring cleaning”) pathways, ultimately resulting in healthier metabolism, better immunity and organ function.

The production of KB occurs when fat is the primary source of energy for the body. This occurs when one is fasting or restricts energy intake (resulting in fat stores being used as energy source), or when modifying the ratio of macronutrients in the diet to favour fat intake whilst reducing carbohydrate intake drastically. In the process, more enzymes needed for fat utilisation are produced, potentially resulting in more efficient fat oxidation, beneficial in weight control.

In a typical ketogenic diet, carbohydrate provides only up to 10 per cent, protein between 15-25 per cent and fats up to 80 per cent of total energy intake in the day. For a 9000 kilojoules daily energy intake, this means approximately 53 g of carbohydrate, 200 g of fat and 79-132 g protein. The production of KB can be monitored by finger prick test (rather that urine test), with concentration varying between 1- 7mmol/L.

A ketogenic diet is therefore a low carbohydrate-high fat (but not high protein) diet. The type of fat consumed is of importance, and so is the composition of the small intake of carbohydrate. Indeed, the carbohydrate foods will provide sufficient fibre, vitamins and minerals if selected from non-starch vegetables and citrus fruit.  

The ketogenic diet has been used to manage refractory (treatment-resistant) epilepsy in patients since the early 1920’s, including in children, with over 750 peer reviewed articles on the topic. This is because KB act as a steady supply of energy for the brain and have an anticonvulsant and antiepileptic effect. For this purpose, the protocols strictly limit carbohydrate intake to a minimal amount (10-20 g daily), which restrict food options and requires careful meal planning, including fibre and micronutrient supplementation. In children following the diet, long term follow-up has shown incidence of stunting, kidney stones and bone demineralisation in 13-20 per cent of patients.

Different protocols of the diet are currently being investigated for the management of other neurological conditions, and prescribed for the control of blood sugar levels in type 2 diabetes. Trials are underway to assess the efficacy of ketogenic diets in the control of glycolytic tumour growth.

When excluding one or more food groups in the diet, it is paramount to consider what nutrients are being jeopardised in the process, in order to ensure adequate supply through savvy meal planning or supplementation. For this reason, it is recommended to seek the advice of dietitians to receive guidance on how to follow such dietary plan for optimal health outcomes.

Dr Veronique ChachayAuthor: Dr Veronique Chachay is from UQ's School of Human Movement and Nutrition Sciences. Dr Chachay's research interests include the nutrient-gene relationship in the context of health and ageing disease, brown adipose tissue recruitment and activation, diet-induced thermogenesis in the management of obesity, the genetic characterisation of individuals following exclusive dietary patterns, as well as the effect of exclusive dietary patterns over time in the context of ageing and longevity.