Everything you need to know about the ketogenic diet
The low-carb, high-fat diet, is said to promote weight loss. But how does it work. And is it safe?
Nutritional science is evolving very fast. We do not know everything, and as is the nature of science, we never will. For those who are experts in the area, it's extremely exciting. The greater understanding that we have through good quality research means that are an array of diets out there that will suit the varied individuals within the populations. There is no one-size-fits-all. In fact for some people, standard healthy dietary guidelines go out the window. The ketogenic (keto) diet is a perfect example, and is something dietitians do advocate, for certain individuals.
■ What is a ketogenic diet?
The keto diet is high in fat, moderate in protein and low in carbohydrate. This involves eating a lot more fat, often lowering your protein intake and reducing your carbohydrate intake to minimal amounts. In other words it's not 'low-carb' which involves cutting out breads, pasta, rice, potatoes etc - it goes a step further.
For example, if you usually eat scrambled eggs on toast for breakfast, a 'low-carb diet' would usually mean reducing the bread from two to one slices. A keto diet would involve eating no bread, and using a lot of oil or butter to scramble the eggs in.
The other important thing to know is that it is not a nutritionally complete diet, and it requires supplementation. It's also rather expensive to follow.
■ What happens within your body on a ketogenic diet?
The body usually fuels itself on a mixture of carbohydrates and fats. The more out of breath we are, the more we use carbohydrate as our main fuel. The brain is different, it only uses carbohydrates. Therefore, when you change your diet to contain extremely low levels of carbohydrates the brain is starved of its main fuel. The body is forced to adapt. It turns on ketogenesis which stimulates the production of ketone bodies from fats. These ketones are then used as the fuel for both the brain and the body.
To be 100pc clear - getting people into ketosis is not an easy process, and keeping them there is often a challenge requiring long-term support from a team of healthcare professionals.
Although there are many conditions and diseases where the benefit of following a keto diet is being investigated, the focus of this article is on sports performance, epilepsy and cancer.
■ Weight loss
Lower carbohydrate diets have been shown to result in weight loss. The keto diet is not a low-carb diet. Despite this fact, a few researchers, and certainly many media reports still seem to confuse the two. True ketosis is hard to achieve and challenging to maintain. Ketosis can be easily switched off by the body if even a few grams of extra carbohydrate are eaten. This isn't a case of breaking the diet and eating a slice of toast. Ketosis can be accidentally switched off by simple errors such as eating a little extra green veg. Achieving ketosis is a very delicate balance.
The keto diet is very much a medical diet as opposed to a weight-loss diet. As studies clearly report that weight loss for many is challenging to maintain, it's unlikely that the keto diet will ever be used by many for weight loss as it too is challenging to maintain.
The reason many lose weight is to be healthier. A nutritionally incomplete diet, where the long-term side effects are not fully known but are considered to be negative, would not achieve a healthier body. If someone would like to lose weight to be thinner, well, there are easier ways of achieving it.
■ The keto diet involves
* counting out grams of carbs, proteins and fats
* manipulating the diet to ensure that the daily food intake contains exactly the right percentage of each
* ensuring that there is a calorie deficit to facilitate weight loss
* buying expensive ketone strips to ensure that you are truly in ketosis
* maintaining this over a period of time in order to lose your desired weight
All of this may be difficult to do while living your life. There are parents out there who help their child follow a keto diet, because that is the best option for that child to reduce seizures. However with weight loss, when there are other options, it's an awfully complicated diet to follow as it is guaranteed to take a lot of time, money, maths, dedication and hits on your social life.
■ Sports Performance
The interest in keto diets in sports is based on the aim of training the body to rely less on carbohydrate. Our stores of carbohydrate within our body are tiny when compared to our stores of fat. Due to this low level of carbohydrate storage, an adaptation to using more fat would, in theory, help the human body exercise for longer. Additionally, it would allow greater fat burning at the same exercise intensity. Could this help performance? There is certainly evidence out there suggesting that if you restrict carbohydrate you will increase your metabolism of fat. However, the evidence that this helps to enhance performance is lacking.
The devout advocates of this approach hang onto a fairly poor study completed in the 1980s. There have been other studies since that showed no benefit, or worse yet, reduced performance at high intensity.
In order to achieve the benefits proposed above, sports nutritionists often encourage athletes to periodize their nutrition. For example, a 'train low' session might be built into an athlete's training programme. This is often misunderstood by many to mean 'training hungry' or 'training before breakfast'. What it actually means is to deplete a person's carbohydrate stores and for them to train on empty stores. When there's no carbohydrate for the body to readily use, the body adapts to use more fat. However, for performance on the days that matter, an athlete's carbohydrate stores are always brought back up again. In other words, you plan your nutrition according to your goals which sometimes means high carbohydrate and sometimes means low carbohydrate.
Epilepsy is a disorder where seizures are caused by abnormal electrical discharges within the brain. Often medications are quite effective at controlling these seizures. In certain circumstances, where medications are not working effectively, the keto diet is considered. Although many people would prefer to use diet to treat a condition rather than medications, this diet is fairly hard-core. It's not a simple case of making a few changes in your diet, it involves overhauling all of it, and sustaining it. It is therefore never considered by healthcare professionals to be the natural alternative to drug therapy.
There was a very large, thorough review, completed recently that included evidence up until March 2015. The good news is that the results were really promising. The problems with the studies conducted and included in this review were typical. For example, they felt that there weren't enough people involved. Unusually, in the area of keto and epilepsy, research only included children. Hopefully there will be more research using adults with epilepsy in the future.
Within the studies included, there were people dropping out because they felt that their seizures weren't improving or because they felt that they couldn't follow the diet. There were some short-term side effects too which did include the likes of diarrhoea, constipation and vomiting.
Considering the dropout rate, the short-term consequences and perhaps the potential for long-term ill-effects on the heart due to the high fat intake, more research is required on more palatable but related diets. For example, a modified ketogenic diet has been found to have similar effects on seizure control as the more restrictive keto diet. However, after this review there was a study published that showed that for patients aged one to two years, seizure outcomes were consistently better in patients consuming the keto diets compared to a modified ketogenic diet.
The number of those free from seizures at three months after diet therapy started was significantly higher in this younger age group (53pc for keto diets, 20pc for modified ketogenic diet). Nevertheless, a medical ketogenic diet has to be followed with full medical support, with regular dietetic input. This is especially important for children who are growing and mismanagement of their diet could have lifelong consequences.
The keto diet has been touted by some to starve cancer of fuel so it cannot survive. Proponents of the diet claim that it works on its own or beside established treatment. At present, the balance and weight of evidence from laboratory and human studies indicates that not alone does the keto diet have no overall beneficial effect on cancers but may stimulate some cancers and can make existing treatments more difficult to bear. There are research papers and theories about how such a diet might theoretically work. However, with no evidence in support of that coming from human trials, in real people, we are only talking about a theory and not proven scientific facts.
When someone is going through treatment for cancer, dietary advice has two focuses. The first being to give your body what it needs to work and prevent weight loss and the second is symptom management. We can see the immediate problems with restrictive keto diets clashing with this approach in a number of ways.
Research (some of it from Irish colleagues) clearly shows that if you are losing weight during treatment, your survival is likely to be much shorter. If you maintain your weight during treatment, you are more likely to have a much more positive outcome from treatment.
Simple changes to your diet can help manage symptoms experienced before, during and after treatment. This is important because if a person is having debilitating side-effects from their treatment, they may not be able to receive all the treatment that was planned for them.
Considering all of this, there are two fundamental issues that cannot be ignored when looking at the keto diet in cancer treatment.
Firstly, research shows that the keto diet is difficult to tolerate as it can cause nausea, vomiting, diarrhoea and tiredness. These are common complaints when someone is going through cancer treatment. If you're trying to reduce the incidence of symptoms, the keto diet is more likely to bring on or worsen these symptoms rather than help a person move through them. This would not only be unpleasant for the person undergoing treatment, but it also reduces their ability to tolerate the full dose of therapy.
Secondly, the effectiveness of most cancer therapy is based around the treatment's ability to find the quickly dividing cancer cells within the body and kill them. Interfering with the actions of the treatment on those cells could actually make treatment less effective. Therefore, it's challenging to understand how keto diets could work without established medical treatment.
The main mantra that all healthcare professionals follow is 'first, do no harm'. At present, there is not enough evidence to advocate the keto diet in any form of cancer care and there is evidence to suggest it can do harm. We've a long way to go in improving cancer treatment but the weight of evidence does not point to keto diets as being one of those ways. Patients would always be well advised to talk to their doctor or dietitian to get the facts more relevant to their own cancer.
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