Ketogenic diets are becoming increasingly popular. As a weight-loss tool, as a performance enhancer and for other health benefits. No matter the reason behind your consideration of the ketogenic diet, it is useful to understand the relevant evidence behind it.
What is the Ketogenic Diet?
The ketogenic diet is a high fat, very low carbohydrate diet.
It involves decreasing your carbohydrate intake to the point that it puts your body into a metabolic state called ketosis.
When this happens, you body becomes more efficient at burning fat for energy. Ketones are also produced, which can be used an energy source.
The standard ketogenic diet traditionally looks something like 80% of calories coming from fat, 15% coming from protein and 5% coming from carbs.
A more common take on the diet now days involves higher protein and could look like 60% of calories coming from fat, 35% from protein and 5% from carbs.
Another common definition of the ketogenic diet that people use is having less than 20g of carbohydrate per day. This is the equivalent of just over just over 1 piece of bread, one tub of yoghurt, 1 medium apple, 1/3 cup of cooked rice or 1 cup of milk. And that’s all you get. For the whole day.
It’s even more difficult when you factor in the small number of carbohydrates coming from some relatively low carbohydrate sources e.g. non-starchy vegetables.
Although 20g is a number that is thrown around, there is no real magic number. It just needs to be low enough for the body to stay in ketosis, so in reality, it could be significantly higher than 20g.
No matter which way you look at it, the ketogenic diet is tough. Say goodbye to pleasures such as potato, fruit, peas, legumes and corn. Not to mention stuff like alcohol, sweets, pie, pasta and chips! So obviously since it is tough, there has to be a reason why people are interested in it.
For Weight Loss
Given the current obesity crisis, the public is becoming increasingly desperate for a magic diet that fixes it all. Some people think the ketogenic diet is just that. While there is evidence to suggest the ketogenic diet is an effective tool in weight loss, the research is in its early days and somewhat flawed.
First off, we don’t just want to lose weight for a mere couple of months. We want weight loss to be maintained for the remainder of our lives. The whole point of a weight loss diet is to be sustainable. The last thing we need is another yo-yo diet to add to the ever-lengthening list.
While it is great that research has found that the ketogenic diet is ‘undoubtedly effective in short to medium term weight loss’, what about the long term? No one wants to lose weight just to gain it all back again. Currently, the longest study in ketogenic diets is 24 weeks in duration.
One of the advantages of a ketogenic diet is that it suppresses appetite to a certain degree, which makes it easier to stay full on a lower number of calories.
One study from 2018 involved ~300 people on a low-carb diet, but in a free-living situation, similar to real life. They were told that they could do whatever they wanted from a protein and fat perspective, but to keep their carb intake as low as they could comfortably maintain it. After 12 months, almost nobody was on a low enough carbohydrate intake to be in ketosis still.
When looking at it from that perspective, while the ketogenic diet can be effective for weight-loss, it is likely only outliers who are able to stick with it consistently enough to reap those benefits and maintain the outcomes.
Firstly, let me make a distinction between weight loss and health. While it is healthy to lose weight (if you are over-weight), and a lot of people losing weight are doing so for health reasons, there is a difference between the use of ketogenic diets for weight loss and for health. When I refer to dieting for health, I am referring to a desire to improve cardiometabolic markers and blood profiles, for the purposes of chronic disease prevention. Weight loss may accompany this, but they are not one and the same.
Evidence suggests that a ketogenic diet can improve the blood lipid profile, contributing to a lowered risk of cardiovascular disease, if followed closely enough.
Outside of cardiometabolic markers, a very low carbohydrate often means a very low intake of carbohydrate nutrients. For example, thiamine, folate, potassium, calcium, magnesium, vitamin A, E and B6 are all at risk of deficiency if the ketogenic diet is not well balanced. A ketogenic diet is also generally lacking in fibre, which is counterproductive to health.
Can a ketogenic diet be set up better in a way that meets these nutrient markers? Yep. But it can be difficult and requires some planning.
For Athletic Performance
High-end athletes have been trialling the ketogenic diet in the pursuit for optimised performance. Sadly, not everyone has seen success. Ketogenic diets may be ergogenic in the context of ultra-endurance athletes. Ultra-endurance refers to gruelling events that last longer than 4-5 hours. For example, marathons upwards of 80km. Yes, such intensive sports exist and yes, some crazy dedicated individuals do compete. While I may not understand someone’s motivations to run for hours on end, I can understand wanting to do it easier and faster.
Often when an athlete runs out of glycogen and hits the wall, their performance drops off significantly. But this is less of an issue for ultra-endurance, since the wall is hit much earlier in comparison to the duration of the event.
Cue ketogenic diet. If the body is constantly exposed to high fat, low carbohydrate, it has the capacity to adapt and more efficiently use fat. However, everyone’s extent of adaptability is different. Where some people might see large success in fat-adaption, some may not. Hence, the diet is not suitable for every athlete.
Even for something such as race-walking which is not a high-intensity sport, the ketogenic diet appears to be slightly sub-optimal. Louise Burke’s Supernova Study demonstrated this.
Furthermore, no matter how well you have fat-adapted, you will never be able to perform at the same intensity as you might on carbohydrate fuelling. This means that for those on a ketogenic diet, high-intensity sprints/jumps will not be as explosive, which may be inhibitory to performance. So because of this, it is sub-optimal for a lot of sports.
Even from an endurance perspective, this aspect is part of how it could make a differs. Imagine you have to go up a steep hill or are at the end of a race and the difference between second and first is a final sprint to finish.
This doesn’t mean the ketogenic diet CAN’T help an athlete. If they go from a poor diet to a well designed ketogenic diet, their outcomes will improve. But if they go from a more optimal diet to a ketogenic diet, at best their performance likely will stay similar, at worst their performance will start to get worse.
Evidence suggests that ketogenic diet can be useful in the management of epilepsy. While there is still a lot we don’t know about this novel treatment, the ketogenic diet has been found useful in the management of epilepsy symptoms so fat.
The Low Down
Ketogenic diets are used for a variety of purposes, and the evidence surrounding ketogenic diets is still emerging. If you are considering following a ketogenic diet, please consult with a dietitian in order to make it is effective as possible to help you achieve your goals, whatever they may be.
Renae Earle is a Masters of Dietetics student at the University of Queensland. Having achieved her Bachelor of Exercise and Nutrition Science with distinction, she is motivated to complete her studies and become an accredited practicing dietitian.
Renae is passionate about evidence-based practice and debunking nutrition myths. She believes that in today’s fad celebrity diet culture, it is increasingly important to deliver the facts. She aims to help people achieve a sustainable and healthful lifestyle by combating the flurry of misinformation offered by tabloids and social media.
In order to achieve this goal, Renae has dedicated herself to the field of nutrition. She is well educated on a wide range of nutrition topics such as supplementation, chronic disease, restrictive diets and metabolism.
Renae has a keen interest in offering personalised nutrition plans that suit the specific needs of her future clients.