Ketogenic Diets: A Dietitian’s Take

Ketogenic diets are quickly gaining popularity these days. You might have read about them or even tried one yourself. But what, really, are they? Are they as simple as cutting out carbohydrates, eating coconut oil, or having bulletproof coffee for breakfast? How do they work? Are they safe? There is so much talk about them, yet there is a lot we still don’t know about them. Here, Beijing United Family Hospital (BJU) Dietitian Jackie Gao draws from her extensive experience of using ketogenic diets as nutrition therapy to answer these questions. 

What are ketogenic diets? 

Ketogenic diets are very high in fat and very low in carbohydrates, and they allow a moderate (not necessarily high) amount of protein. Many guidelines for healthy eating recommend that a healthy diet should derive 45-65% of energy from carbohydrates, 20-35% from fat, and 15-25% from protein to reduce your risk of developing chronic diseases. A ketogenic diet, on the other hand, can range from deriving as little as 6% of energy from carbohydrates and as much as 90% energy from fat. 

Currently, there are four major ketogenic diets with published evidence supporting their use, namely the classic ketogenic diet, the modified Atkins diet, the low glycemic index (GI) diet, and the medium chain triglyceride (MCT) diet. The classic ketogenic diet dictates that a person should eat a 4:1 ratio of fats to proteins and carbohydrates. This is almost quadruple the amount that most healthy-eating guidelines recommend.

How do ketogenic diets work? 

Put simply, a ketogenic diet limits carbohydrate intake so much that it mimics a state of starvation. The body needs carbohydrates to fuel the brain. When our body is starved of carbohydrates, the brain has to switch to an alternative fuel source. The body thus produces ketone bodies by burning fat that we consume or that is already stored in the body. This process is called ketogenesis, and you are said to be in a state of ketosis.

Our bodies normally don’t produce ketone bodies unless they have run out of glucose (which comes from carbohydrates). This is what happens during times of starvation. When ketone bodies are produced, they will be detectable in your breath (you can smell a fruity smell), your urine, or your blood. It is not hard to achieve ketosis as long as your carbohydrate intake is low enough, but it’s very easy to come out of ketosis if you happen to consume an even small amount of carbohydrate over the limit. Many people trying to follow a ketogenic diet may not realize that avoiding pasta and rice is not enough to induce ketogenesis, and that eating fruit can potentially end the ketogenesis. Too much protein can also lead to lower levels of ketosis.

What do ketogenic diets look like? 

Think about the classic food pyramid for healthy eating. Whole grains are at the bottom, forming the base of our diet, and oils are on the top, needing to be eaten in moderation. In a ketogenic diet, the food pyramid is almost like that but in reverse. A normal low-carb diet firstly excludes all foods and drinks with added sugar, such as biscuits, chocolate, and juice. This change may already make you feel better about yourself. A ketogenic diet goes further than this and limits most grains (e.g. pasta and rice), dairy, most fruits, and starchy vegetables (e.g. sweet potatoes and corn). 

For example, on a less restrictive modified Atkins diet, one can only have 15-20 g of carbohydrates for the whole day. This means no more than one large apple or a maximum of two slices of bread. In addition, you can’t overindulge in protein (e.g. meat, chicken, fish, eggs, nuts, and seeds) and all your proteins need to be cooked or served with a lot of fat such as oil, butter, heavy cream, or mayonnaise. The only vegetables and fruit that you can eat must be very low in carbohydrate (e.g. strawberries) or high in fat (e.g. avocado). It’s not hard to see that, on a restrictive diet like a ketogenic diet, you’re missing a lot of vital vitamins and minerals.

What are ketogenic diets used for?

Ketogenic diets have been used since the early 1900s to treat epilepsy. Many studies over the years have shown similarly positive results in improving seizures for patients who used a ketogenic diet in combination with medications. Previously, it was considered a last resort when a number of anti-epileptic medications failed, but now it’s highly recommended for patients who don’t respond to two or more anti-epileptic medications – even in infants (younger than two years of age). The ketogenic diet is also the first line of treatment for conditions such as glucose transporter 1 deficiency syndrome (Glut1DS) and pyruvate dehydrogenase deficiency (PDHD), where glucose cannot be utilized and seizures occur.  

While there are many studies demonstrating that a ketogenic diet results in greater weight loss than low-fat diets, at least in the short-term, fewer data are available to demonstrate long-term success.

From a heart health perspective, a report from the American Heart Association, the American College of Cardiology, and the Obesity Society concluded that there isn't enough evidence to say whether most low-carbohydrate diets provide heart health benefits.

But is it the ketone bodies that explain why ketogenic diets are helpful for autism, Alzheimer’s, and brain tumors? The answer is largely unknown. Many researchers are trying to find out the answer to the mechanism of action but a lot is still unknown. Because many studies have been done on animals or very small groups of test subjects, researchers still don’t know how it will work on our human bodies and can’t make recommendations for the general population. 

Side effects

Within the first week of being in ketogenesis, you may experience nausea, vomiting, bad breath, reduced appetite, fatigue, and/or hypoglycemia-like symptoms (e.g. shakiness, hunger, dizziness, and headaches). In the longer term (a few weeks to months), you may experience elevated cholesterol and triglyceride levels, constipation, nutrient deficiencies, increased risk of poorer bone health and kidney problems, and, more seriously, ketoacidosis, a dangerous condition that requires hospitalization.

A very recent Lancet publication demonstrated that a low-carbohydrate diet consisting of less than 30% of total energy coming from carbohydrates can shorten life by four years, two to three years less for those who get 30-40% of their energy from fat. 

What should I do first if I want to try a ketogenic diet?

Whichever version of the ketogenic diet you want to try, you should never do it alone. Before you consider doing it, you need a medical doctor and a clinical dietitian to perform a set of tests to screen for conditions. They need to ensure you are safe to start and don’t already have symptoms that may worsen when you start the diet. These include, but are not limited to, defects in metabolizing fat, acid reflux, constipation, and high blood lipids. Your doctor and dietitian will also monitor your progress. 

Furthermore, you are not a good candidate if you simply love your carbohydrates and don’t want to give them up because the change in diet is so drastic you'll find it difficult to follow in the long run. 

In human subjects, the effects of a very prolonged ketogenic diet are, as yet, not well investigated. For this reason, ketogenic diets may be used safely only for a limited period (from a few weeks up to three months). 

What is required for success on a ketogenic diet?

If you follow a true ketogenic diet, more than just your diet will change. Ask yourself if you are ready to accept the following before throwing yourself into this lifestyle change:

• A considerable amount of commitment (such as planning ahead, cooking from scratch using mostly whole foods and fresh ingredients, and following the diet plan strictly);

• Minimal amounts of carbohydrate served with plenty of fat at each meal and snack; 

• Limited diet choices, especially when eating out;

• The fact that it is difficult to maintain ketogenesis;

• The fact that you will have to learn the carb contents of what you eat, and always read food label if there is one; 

• Close monitoring of ketone levels and blood sugar levels; and

• You will have to take daily medications and/or supplements to protect your bones and kidneys and to prevent nutrient deficiencies; 

Take home messages 

- Ketogenic diets are very low in carbohydrates and high in fat and provide a moderate amount of protein.

- They involve a considerable amount of commitment and possibly significant diet and lifestyle changes.

- Ketogenic diets have unwanted short- and long-term side effects.

- Ketogenic diets are not designed for everyone.

- Do not attempt a ketogenic diet without supervision from a doctor and dietitian.

- If you have already started a ketogenic diet, seek your doctor and dietitian’s advice to ensure you are doing it right. 

Jackie Gao is a Chinese-born, Australian-trained dietitian and nutritionist. To make an appointment with her, please call our service center at 4008-919191.

• Want to read more diet tips from Jackie? Here you go. 
  

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• Want to up your fiber intake? Here's what a high-fiber diet looks like. 

References:

1. National Health and Medical Research Council (2013) Australian Dietary Guidelines. Canberra: National Health and Medical Research Council.

2. National Health and Medical Research Council, Australian Government Department of Health and Ageing, New Zealand Ministry of Health. Nutrient reference values for Australia and New Zealand including recommended dietary intakes. Canberra: Commonwealth of Australia; 2006.

3. Chinese Nutrition Society. Chinese Guide to Healthy Eating. 2016.

4. US Department of Health and Human Services, US Department of Agriculture. Dietary Guidelines for Americans 2015–2020.

Eighth edition. https://health.gov/dietaryguidelines/2015/guidelines/ (accessed Sep 24, 2018).

4. Wilder RM. The effect of ketonemia on the course of epilepsy. Mayo Clin Bulletin 1921;2:307–308. 

5. Kossoff EH, Zupec-Kania BA, et al. Optimal clinical management of children receiving dietary therapies for epilepsy: Updated recommendations of the International Ketogenic diet Study Group. Epilepsia Open, 3(2):175–192, 2018 doi: 10.1002/epi4.12225 

6.Kim JA, Yoon JR, Lee EJ, et al. Efficacy of the classic ketogenic and the modi-fied Atkins diets in refractory childhood epilepsy. Epilepsia 2016;57:51–58. 

7. Jensen MD, et al. 2013 AHA/ACC/TOS guidelines for the management of overweight and obesity in adults. Journal of the American College of Cardiology. 2014;63:2985.

8. Seidelmann S, Claggett B, et al. Dietary carbohydrate intake and mortality: a prospective cohort study and meta-analysis. Lancet Public Health 2018; 3: e419–28. 

9. Bueno N.B., de Melo I.S., de Oliveira S.L., da Rocha Ataide T. Very-low-carbohydrate ketogenic diet v. Low-fat diet for long-term weight loss: A meta-analysis of randomised controlled trials. Br. J. Nutr. 2013;110:1178–1187. doi: 10.1017/S0007114513000548. 

10. Antonio Paoli. Ketogenic diet for obesity: Friend or Foe? Int J Environ Res Public Health. 2014 Feb; 11(2): 2092–2107. Published online 2014 Feb 19. doi: 10.3390/ijerph110202092