What is the keto diet?
A high-fat, low-carb approach to nutrition, the basic principle behind the keto diet is to limit carbohydrate intake (such as pasta, bread and potatoes) to between 20–50g per day so your body enters a state called ketosis, which happens when your body doesn’t have enough carbs to burn for energy so turns to its fat stores instead.
Scientific studies of keto diet health benefits aren't exactly in abundance. But that's not to say there aren't health benefits associated with the keto diet – only that long-term research on its effects is in its infancy and that – like any diet – it may not be for everyone.
We know for sure that dietary fat isn't necessarily a bad thing, while scientific research has shown that other substances such as sugar can absolutely have as much of an impact on your health and body weight as fat.
Interestingly, when your body enters ketosis, it doesn't just burn fat reserves for energy, it also releases something called ketones. As a review from the University of California puts it, 'besides glucose derived from carbohydrates, ketones from fat are the only fuel the brain can use' suggesting that the keto diet could well have brain health benefits too.
Intermittent fasting can also be used to achieve ketosis.
Different keto diets explained: Clean keto, dirty keto, lazy keto
There are different versions of the keto diet, with slightly different rules around what you can and can't eat. Here are the three main ones:
Clean keto is when you focus on nutrient-dense food. Fat-rich protein, eggs, nuts and non-starchy vegetables are all part of the clean keto diet. Crucially, clean keto stays away from processed foods and carb intake is never more than 50g a day.
Dirty keto allows you to eat processed food. Takeaways and ready meals can form part of the dirty keto diet, although the restriction on carbs remains. The problem with this diet is you might miss out on vital nutrients and vitamins from eating poor quality food.
Lazy keto is when you stick to the main principles of the keto diet but don't bother with the careful calculation of portions. Effectively you keep your usual eating habits and only focus on restricting carbs. Lazy keto is an easy option if you're looking for a new diet but don't want to spend the time planning your daily meals to the gram.
What’s the science behind the keto diet?
Much of the research around the keto diet is still in its infancy as scientists seek to build up data over time to discover the long-term and short-term benefits and impacts of limiting carb intake.
The basic principle of the keto diet is to achieve weight loss by restricting carbs, and thus tuning your body to burn its fat reserves instead. Studies have found that this can help in combating diabetes and epilepsy in children.
Research published by the journal Experimental & Clinical Cardiology on the long-term effects of a ketogenic diet in obese patients confirmed it is an effective weight-loss approach. Scientists looked at how the bodies of overweight patients changed over a 24-week keto diet, consisting of a daily intake of 30g carbohydrates, 1g/kg body weight protein, 20% saturated fat and 80% polyunsaturated and monounsaturated fat.
While the report concluded there are, 'beneficial effects of a long-term ketogenic diet' and that it, 'significantly reduced the body weight and body mass index of the patients,' all of the test subjects were already medically obese, so the effect may not be as dramatic if you not particularly overweight. Patients also showed lower cholesterol and blood glucose levels as a result of the diet.
Remarkably, another study published in the The American Journal of Clinical Nutrition concluded that the keto diet itself doesn’t reduce body fat at all. What causes weight loss, they say, is the diet’s knock-on effects, such as when people reduce their sugar intake and stop eating processed foods simply because they are more conscious of what they’re eating.
Is the keto diet good for your brain?
While the brain can use ketone bodies from fat to fuel its energy demands, there are few long-term studies that outline the real brain health benefits of the keto diet. There are suggestions the keto diet can help in the treating of drug-resistant epilepsy in children, but as research published in Frontiers in Neuroscience states, 'less restrictive and more palatable diets are usually better options for adults and adolescents'.
Studies in animals have shown that the keto diet could help in the treatment of depression, while research is being conducted into how a ketogenic diet can possibly combat amyloid plaques in the brain that cause Alzheimer's disease.
Schizophrenia and bipolar disorder are also being researched along with the keto diet, although no substantial results have yet been published. So while there may not be conclusive evidence at this stage, it's an area of interest that is being more deeply researched as you read this.
Is the keto diet safe?
While the keto diet has many fans, others believe it is a 'fad' that science has not totally got to grips with. An interview published by University Chicago Medicine suggests the diet 'restricts fresh fruits and vegetables, whole grains and low fat dairy that can help with long term weight loss and overall health'.
Potential harmful effects of the keto diet include:
Low blood pressure
Increased risk of heart disease
There is also an issue with a condition known as 'keto flu', which can occur when your body adapts to ketosis. This is when the lack of carbohydrates lead to symptoms such as decreased energy, dizziness, an upset stomach and mood swings,.
In general, the keto diet is totally safe. However, everyone is different and you should always listen to your own body when making any drastic changes to your diet.
The major downside to the keto diet, however, is simply that its restrictive nature can make it difficult to stick to – especially if you’re doing Clean Keto. After all, planning every meal and monitoring your carb intake to the gram is very difficult. More often than not people slip out of their regime, thus defeating the objective.
Should athletes do the keto diet?
There is no proven benefit between athletic performance and the keto diet. In fact, it almost works counter-intuitively to what athletes’ bodies require during exercise. While you can argue the keto diet is good for weight loss, sporting performance needs carbohydrates.
As lecture notes from the British Medical Journal states, 'the key factor in coping with the heavy demands of exercise faced by elite athletes seems to be carbohydrate intake'.
Studies show that athletes benefit from:
200g to 300g of carbohydrates consumed three to four hours before the athletic event
30g–60g carbohydrates per hour during exercise
1.0–1.5g/kg of bodyweight carbohydrates during the first half hour after exercise, and again every two hours for four to six hours in order to replace liver and muscle glycogen stores
So… Should You Do the Keto Diet?
The keto diet is scientifically proven to be effective for fat loss for those with a high BMI. However, all strict diets require commitment and careful planning. Regardless of your body weight or shape, diets ahve the potential to be harmful if you dramatically change your regular food consumption overnight.
As science looks ever more closely at this form of high-fat, low-carb diet, we will only improve and develop our understanding of the health benefits around keto. But just like any diet there is no ‘one size fits all’ solution.
As clinical dietician Rachel Kleinman says: 'There’s not one diet that’s good for everyone. Do your research, consult a dietitian, discuss with your doctor, and make sure you’re being safe.'