1 September 2017


No. Not a music group. But ketones are creating a lot of noise. They are a kind of fuel our liver produces from fatty acids (from what we eat or body fat stores), when glucose is severely restricted. Dietary regimens that stimulate the production of ketones are known as “ketogenic diets”. What are their health effects?

Randomised controlled trials give us some clues. Ketogenic diets typically require people to limit their total carbohydrate intake to less than 10% of energy (less than 50g a day for an adult), and recommend fat provides around 80% of energy. This means severe restriction of: 

  • most fruits 
  • starchy vegetables (carrots, corn, peas, pumpkin, potatoes, etc) 
  • cereal-based foods (bread, breakfast cereals, pasta, rice, etc) 
  • legumes (beans, chickpeas, lentils, etc) 
  • milk and yoghurt. 
For a typical adult, 10% of energy, or 50g of carbohydrate a day, is equal to 2 slices of bread plus 1 piece of fruit. Instead of carb-containing foods, people on a ketogenic diet mostly eat: 
  • meat, seafood, poultry 
  • eggs 
  • cheese 
  • butter and cream 
  • fats and oils 
  • low-carb vegetables (greens, onions, peppers, etc) 
  • low-carb fruits (berries). 
As it’s difficult to get all of the essential nutrients eating this way, people on a ketogenic diet need supplements.

Fatty meats  
Epilepsy A ketogenic diet has been trialled in children with chronic epilepsy. Children are typically given a diet that provides 80% of daily energy from fat, and the remainder from protein and carbohydrate (typically, 10% from each). A recent Cochrane review determined that after following a ketogenic diet for 3 months, seizure rates may decrease by up to 85% in some (but not all) children. But all studies included in the review also reported adverse effects – vomiting, constipation and diarrhoea plus other adverse effects. A recent study determined that while medically effective “The study did not find any improvements in quality of life”. So, while a ketogenic diet may help some children with epilepsy, it’s no panacea. However, if you have a child with severe, frequent seizures, you may wish to try a ketogenic diet under very careful medical and dietetic supervision.

Cancer therapy Certain kinds of cancer cells prefer to use glucose as a fuel. Therefore, in theory, reducing blood glucose levels may help in the management of certain kinds of cancer by starving them of fuel. A recent systematic review examined all the available evidence in people (not rats). No randomised controlled trials were identified, but 15 other lower-quality clinical studies, case-control and cohort studies incorporating 330 people were available. The authors concluded “In contrast, to the considerable attention from researchers, physicians and the media for its potential role in cancer treatments, evidence on benefits [of ketogenic diets] regarding tumor development and progression as well as reduction in side effects of cancer therapy is missing.” The bottom line – despite the hype, much more research is needed.

Ketogenic diets for weight loss While not new, ketogenic diets are at present one of the most popular weight loss diets around the world. Fortunately, over the past 2 decades, there have been a significant number of randomised controlled trials comparing (high-fat) ketogenic diets to low fat diets, and a systematic review and meta-analysis was published recently. It identified thirteen studies incorporating 1415 people and determined that over 1–2 years (medium-term), people consuming the ketogenic diet lost more body weight, and their blood pressure and fats improved compared to people consuming a low fat diet. The authors concluded “... in the long term and when compared with conventional therapy, the differences appear to be of little clinical significance, although statistically significant.”

So while the ketogenic diet may be an alternative to other diets under certain circumstances it is not necessarily superior in the long-term; we must as usual keep in mind the simple fact that one size does not fit all. Because food plays such a pivotal role in our family and social lives, ketogenic diets can be disruptive and long-term adherence and enjoyment of food (one of life’s pleasures) are frequently issues. And there are side effects, especially in the beginning until the body adjusts, including constipation, headache and fatigue.

You can listen to Alan discuss ketogenic diets on Health Professional Radio, here.

 Dr Alan Barclay  

Alan Barclay, PhD is a consultant dietitian. He worked for Diabetes Australia (NSW) from 1998–2014 . He is author/co-author of more than 30 scientific publications, and author/co-author of  The good Carbs Cookbook (Murdoch Books), Reversing Diabetes (Murdoch Books), The Low GI Diet: Managing Type 2 Diabetes (Hachette Australia) and The Ultimate Guide to Sugars and Sweeteners (The Experiment, New York).