Ketogenic dieting: the low carb diet that celebrities like Gwyneth Paltrow, Kim Kardashian-West and Megan Fox have all pledged themselves to.
However, like with many diets, we're always left questioning whether they actually work or not.
Like, why follow a ketogenic diet? Who should eat a ketogenic diet? And in terms of a low carbohydrate diet, is this really the best way to lose weight?.
Here, Dr Alan W Barclay, consultant dietitian, nutritionist and co-author of The Good Carbs Cookbook, answers all your questions to see if this diet is, in fact, any good for you.
What is the ketogenic diet?
A ketogenic eating pattern is very low in carbohydrates and moderate in protein, meaning a high percentage of total energy (kilojoule) intake comes from fat.
As fat is the main source of energy being consumed, the body must then use this (that is, break it down) as its main energy source or 'fuel'. When dietary fat is metabolised for energy, by-products called ketone bodies (molecules that are made by the liver from fatty acids) are produced which are used up by the body's tissues, muscles and the brain. This process is known as ketosis.
The body can enter ketosis during times of severe energy restriction (such as during fasting or starvation) or prolonged intense exercise, or when carbohydrate intake is reduced to around 50g per day, or less – the equivalent of around two slices of bread, and a banana.
Short-term side effects of ketosis can include fatigue, bad breath, nausea, constipation and headaches.
How safe is ketogenic diet?
The most common side effects of the diet are vomiting, constipation and diarrhoea. While less common, other adverse effects include increased respiratory tract infections, pancreatitis, gallstones, fatty liver, high cholesterol, acidosis, dehydration, decreased bone density, extended hospital stay, hunger and abdominal pain.
It's important to note that we only know medium term (less than two years) health effects and do not know what the long-term (greater than two years) health effects are.
The ketogenic diet for weightloss
Following a keto diet will undoubtedly result in short-term weightloss, which probably comes down to a reduction in total energy (kilojoule) intake, the depletion of liver and muscle glycogen stores and associated water, and a reduced appetite (which is a side effect of metabolising ketones, and also due to satiety associated with eating foods containing fat and protein).
But the key to maintaining a healthy weight in the long-term is an eating pattern that is sustainable over time. With this in mind, dietary recommendations should always be tailored to an individual – as everyone is unique, and what works for one person, may not work for another. That is, there is no one-size-fits-all approach when it comes to achieving and maintaining a healthy weight.
Who benefits from ketogenic diet?
Children with severe epilepsy who have not responded to conventional therapy may wish to trial the diet under careful medical and dietetic supervision.
When ketogenic diet doesn’t work
If you don't consume less than 10% of energy from carbohydrate, you won't go into ketosis, so the diet won't work. For an adult that means consuming no more than 50 g of carbohydrate per day, and for children it means less due to their typically lower energy requirements. For most people, this is very difficult.