The ketogenic diet is by no means a new diet, but has recently gained a lot of attention in the world of science and nutrition. You may have heard this diet referred to as ‘keto’ or ‘low-carb-high-fat (LCHF)’.
So why the craze about keto? And what are the implications for gut health?
What is a ketogenic diet?
Put simply – a ketogenic diet is low in carbohydrate (between 5-20% of total intake), and high in fat (up to 75% of total intake). It is sometimes used to improve seizure management in epilepsy, particularly in children. More recently it has become a popular diet for weight-loss.
Normally, our brain uses glucose as its main fuel source. This glucose is provided to the brain via the breakdown of carbohydrate foods such as bread/grains, dairy products, fruit, and starchy vegetables. When these foods are essentially eliminated on a ketogenic diet, there is insufficient glucose available as fuel. The brain then relies on chemicals called ketones as an alternative fuel source. These ketones are produced via the breakdown of dietary fat from foods such as nuts, avocado, eggs, and oil.
This diet ultimately results in weight loss due to both an energy deficit (i.e burning more calories than you consume), and potentially burning fat more effectively. A ketogenic diet has been associated with benefits such as weight loss and reduced inflammation. However, there are a few key considerations to note.
Low-carbohydrate = low-fibre
Since a ketogenic diet usually provides 20-50g carbohydrate per day, it is virtually impossible to meet your daily fibre requirements (without the use of supplements). The low-fibre intake of a ketogenic diet can result in constipation, which can then cause symptoms like stomach cramps and nausea. This may particularly impact the gut symptoms of those with IBS, especially constipation-predominant (IBS-D).
Low-fibre = low-prebiotics
Being low in fibre means a ketogenic is consequently also low in prebiotics. In simple terms prebiotics are a type of fibre we can’t digest (see prebiotic article for more details). They promote the growth + activity of good bacteria in the large intestine. Certain FODMAPs including fructans, galacto-oligosaccharides (GOS), and inulin hold prebiotic effects. This is one reason why a low FODMAP diet is not a long-term diet. Long-term restriction of prebiotics, such as on a ketogenic diet, can negatively impact gut health and immune function.
High fat and gut health
A ketogenic diet is very high in fat, which can trigger gut symptoms, due to an increase in gut motility. This is particularly common for those with IBS, as fat can be a common symptom trigger (see article on dietary fats and IBS). Dietary fat should make up 20-35% of our dietary intake, so increasing this to as high as 75% may likely provoke gut symptoms such as abdominal cramping and diarrhoea.
So is a ketogenic diet necessary?
For most individuals, no. As mentioned earlier, a ketogenic diet does have its place in the clinical setting for the management of epileptic seizures in about one third of patients. A ketogenic diet has shown positive results for weight loss, inflammation, and the management of some health conditions. However, there are more sustainable and safe ways to achieve these outcomes.
The body will only benefit from, and remain in, ketosis if the diet is strictly followed. This means you can’t be flexible and just include higher carbohydrate foods when you feel like it. as the body slips out of ketosis. Returning to a higher carbohydrate diet will more than likely result in rebound weight gain, often quite rapidly.
The diet is very restrictive and may be difficult to follow long-term, particularly in regards to social situations. It can be hard enough to eat out on a low FODMAP diet, let alone a low FODMAP ketogenic diet. As explained through this article, the LCHF composition of the diet can have negative impacts on gut health. We know now more than ever that our gut health is central to overall health. Good gut health is particularly important for those with GI conditions such as IBS.
There is an abundance of misleading and incorrect nutrition advice information circulating the internet. Often this advice comes from individuals who don’t have the qualifications to provide it. If you do choose to follow a ketogenic diet, ensure this is done under the supervision of a GP and Accredited Practising Dietitian (APD).
Start feeling better now! By signing up to The FODMAP Challenge you will receive meal plans, recipe ideas, and regular support with other resources, such as a private Facebook group, to make this as easy for you as possible.