Ketogenic Diet: What Is It? Does It Work? Is It Just a Fad?
Naturally, this will be one of the longer articles on this website but I will try to keep it easy to navigate and as straight-forward as possible. Hopefully this will allow you to read the whole thing and consume as much information as possible, or easily navigate to certain sections to answer certain questions you may have. There is a ton of information out there on ketogenic diets and it would be impossible to go in depth on all of it but hopefully this will help you sift through the not so evidence-based claims while learning about the real benefits.
Ketogenic Diet: What Is It?
Like it or not, the ketogenic diet works and is not going away any time soon..
Ketogenic diets may also be referred to as low-carb-high fat (LCHF) diets or the Atkin's diet. A ketogenic diet is a diet that is composed of high-fat, moderate protein, and low-carbohydrates. There are many different variations of ketogenic diets all with different ratios of fat-carb-protein but they all have one thing in common; high fat and extremely low carbohydrates (usually <50g carbs/day). Recently, more variations of the ketogenic diet have surfaced and the supplementation of medium-chain triglycerides (MCTs) has become extremely popular. MCTs are a type of fat found heavily in coconut oil and can act as an extremely fast energy source that is almost never stored. This property of MCTs is extremely advantageous for a ketogenic diet because it is a way to bypass the severe caloric restriction and still remain in ketosis. Another variation of a ketogenic diet is called the modified Atkin's diet. This diet is a ketogenic diet that is less restrictive and allows for normal protein intake and daily calories (1). The modified Atkins diet will also allow for the intake of vegetables with a low glycemic index and is much easier to stick with than a strict ketogenic diet.
Ketogenic diets have been used since the 1920s. These low-carb diets were originally used as a therapy for epilepsy where they have experienced great success therapeutically. By the 1960s ketogenic diets had become a very common and successful therapy for weight loss and obesity. Recently, the ketogenic diet has shown benefits for dozens of other conditions and the research is rapidly growing and accumulating. Some of the more recent conditions that ketogenic diets have been shown to be beneficial for include diabetes, acne, neurological diseases, cancer, cardiovascular disease risk, and many more (2). These conditions as well as other benefits will be discussed more in-depth below.
Typical Macronutrient Ratios for the Ketogenic Diet:
Fat: 60-75%
Protein: 15-30%
Carbohydrates: 10-25%
Ketosis: How Does It Work?
The main goal of a ketogenic diet is to put the body in a state of ketosis and remain there. Ketosis occurs when the body has minimal metabolism of carbohydrates and stops using sugar as fuel and begins metabolizing fat instead. Since sugar is the body's preferred energy source, this energy metabolism shift from carbohydrate to fat is forced upon the body when it runs out of carbs after 3-4 days of the ketogenic diet or fasting. This metabolization of fat allows for energy to be derived from a product called ketone bodies instead of relying on glucose (normal energy source). Ketone bodies are made in the liver as the result of the breakdown of fat and can be tested in the blood as acetoacetate, beta-hydroxybutyrate, and acetone (2) .
The burning of fat/ketone bodies instead of carbs/glucose as energy for cells may have several mechanisms as a therapeutic option for wide range of diseases, and each mechanism may be different. When in ketosis, the ability of the body to tap into adipose fat stores (e.g. belly fat), clear and renew damaged cells (apoptosis/autophagy), balance out brain energy spikes, and give different cells a "break" from normal glucose metabolism are all some of the proposed mechanisms for certain conditions (1). In addition to these there are many other mechanisms that may explain the positive effects of the ketogenic diet which will be reported with more detail below.
Are there any Risks?
Ketogenic diets can be extremely beneficial in many individuals, but they are not for everyone and may come with adverse effects. Short-term side effects are generally mild and can include gastroesophgeal reflux (GERD), constipation, low blood sugar, and lethargy (at the beginning stages) (1). Serious adverse effects with the ketogenic diet are rare and the diet is generally safe for healthy individuals. One of the main complaints commonly seen with people first starting the ketogenic diet is fatigue, irritability, and excess hunger. These side effects are usually reported as a "sugar withdrawal". Depending on health and past diet status, these complaints will generally go away once your body becomes accustomed to no longer running off of carbohydrates and sugar. Overall the ketogenic diet is usually safe but should be monitored especially if you are suffering from a current metabolic condition.
What Does It Work For?
Weight Loss & Body Composition:
The ketogenic diet has been an excellent tool for weight loss and body composition improvement for decades. Not only is it an excellent way to lose weight, it can help keep the weight off. A meta-analysis from the British Journal of Nutrition reported that the ketogenic diet is better for long-term weight loss than a standard low-fat diet (4). The ketogenic diet has also been shown to help improve body composition and protect muscle while losing fat in overweight women when combined with a resistance training program (5).
The exact mechanism of why a ketogenic diet is beneficial for weight loss and body composition is not a simple one. There is likely multiple reasons for the diet's body composition benefits:
Reduction in appetite (6)
Reduction in fat storage (7)
Increase in fat burning (8)
Increased metabolic energy use (2)
Epilepsy
One of the first and most common uses of the ketogenic diet is epilepsy. The ketogenic diet has been shown to be safe and effective in children, adolescents and adults with epilepsy (9). More recently, the modified Atkin's diet has also been shown to be as safe and effective for epilepsy (10). The modified Atkin's diet may be a better option for individuals with epilepsy because it is less strict and allows for a more adequate intake of vegetables and other micronutrient dense options.
Neurological Diseases
The ketogenic diet has been shown to protect the cells of the nervous system in conditions that may have abnormal cellular energy utilization. This may be due to the diet's ability to decrease free radical formation and inflammation seen with standard sugar metabolism. Another possible mechanism could be due to the regulation of electrical signals in the brain and other cells of the nervous system (2).
Currently, the ketogenic diet has been shown to possibly be beneficial for the following neurological conditions:
Amyotrophic Lateral Sclerosis (ALS): The number of pharmacological treatments of ALS is extremely limited so finding any treatment option with any efficacy is important. Research suggests that the ketogenic diet may improve motor function, energy utilization, and protect neurons in mice models of ALS (13).
Alzheimer's Disease: Ketogenic diet can protect against Alzheimer's disease risks and also improve memory with mild impairment (11) (12).
Parkinson's Disease: The main cause of Parkinson's disease is not completely understood but it is associated with damage to a certain type of neuron and neurotransmitter (dopaminergic, dopamine). Although in the early stages of research, some signs may indicate that the ketogenic diet could play a role in protecting these dopaminergic neurons against degeneration and serving as a therapeutic option for the disease (14).
Exercise Performance
There is great debate about the ketogenic diet and how it may affect exercise performance. Years ago it was thought that the ketogenic diet was an absolute detriment to exercise performance and would cause the destruction of muscle and decline in performance. Recently, the myth that the ketogenic diet is something that should never be followed when exercising has been completely debunked. Some "less-informed" and "more-traditional" individuals who usually come in the form of self-taught personal trainers still bash the application of the ketogenic diet for low-moderate intensity exercise despite what the science says. Unless you are a highly trained competitive power or speed athlete that relies solely on quick burst of (glycolytic) energy to put you ahead of the competition, the ketogenic diet will likely only cause a small decrease in performance (15). In fact, a study on cyclists suggests that the long-term application of the ketogenic diet is favorable for endurance athletes and leads to more fat loss and decreased muscle damage after exercise. A possible mechanism for this benefit is the ketogenic diet allows the body to use an alternate fuel source by burning visceral fat stores and burning more ketone bodies instead of glucose- which will likely result in less damage to muscle. (16). Studies have also noted improvements in other performance and exercise measures for certain populations. For example, a study that looked at body composition, power, strength, and hormonal profiles in college aged men on a resistance training program showed that the ketogenic diet improved body composition and increased testosterone levels while not affecting power or strength when compared to a standard diet (17). Another study showed that the ketogenic diet could protect against the loss of muscle while increasing fat burning in overweight women (18).
Although good for performance under certain conditions, it is important to remember that the performance benefit from the ketogenic diet may only be seen in endurance athletes at low-moderate intensity and may actually have a small negative effect if you are looking to build muscle or increase power (15). However, this negative effect may not apply to all circumstances and the ketogenic diet has been shown to have some benefits beyond endurance performance. The positives and negatives of the ketogenic diet are extremely variable depending on the individual's genetics, goals, and training program. Overall, if your goals are to increase power, strength, or muscle size the ketogenic diet may not be right for you. If you are struggling with losing fat and your main goal is to lose fat without losing your lean muscle, the ketogenic diet may be worth a shot.
Cancer
One thing that most cancer cells have in common is that they can only use glucose (sugar) for energy and cannot run off of ketones (fat). The reason that the ketogenic diet can be a beneficial adjuvant therapy to standard cancer treatments is theorized to be due to decreasing the glucose available to the cancer cell thus decreasing its ability to replicate and making it more susceptible to damage from chemotherapy and radiation (1). A recent systematic review of studies on animal studies of various types of cancers suggested that the ketogenic diet may inhibit cancerous cell growth and increase overall survival times (19). Although the ketogenic diet shows promise as an adjuvant therapy for cancer, there is not nearly enough research to fully implement it into practice consistently. There are still many people who have claimed successful results using this diet for cancer and hopefully the current clinical trials will provide more robust evidence and allow for the ketogenic diet to be a more common strategy in cancer treatment.
Acne
High sugar foods have been linked to the development of acne and theres is nothing the ketogenic does better than limit sugar. The mechanism of the possible ability of the ketogenic diet to improve acne is very complex and involves insulin and other hormones that respond to sugar. Overall, the evidence that the ketogenic diet improves acne is limited and needs to be confirmed in more studies (20).
Diabetes
The ketogenic diet as a possible treatment for diabetes has been controversial. Many more traditional physicians may theorize that it can be extremely dangerous to patients due to extremely low blood sugar. This is not completely true. The ketogenic diet has been shown to be effective for diabetes but should be carefully monitored by a physician to avoid any unwanted adverse effects. Low carbohydrate diets have been shown to be more effective than the standard low glycemic index diet for improving blood sugar control, reducing diabetic medication usage, and reversing type II diabetes (21). A more recent study also showed a low-calorie ketogenic diet to be more effective at controlling blood sugar than a standard low-calorie diet (23). Although the ketogenic diet is effective for diabetes, it is important to remember that a physician's guidance and monitoring should be used when using the diet for this purpose.
Cardiovascular Risk
Blood lipid levels like triglycerides and cholesterol are a common measurement to use to assess an individual's risk of cardiovascular disease. When compared to low-fat diets, low-carbohydrate diets have been shown to improve the blood lipid profile in a way that would resemble a lower risk for cardiovascular disease (decrease triglycerides, increase HDL) (22). More studies are needed to confirm this phenomena and this effect does not appear to be beneficial in children.
What to Expect:
There is no strict way to follow the ketogenic diet, although there are guidelines to ensure that a state of ketosis is reached. A general guideline for carbohydrate intake is around 20-60 grams per day, with fat and protein filling in the rest. Low levels of energy, fatigue, brain fog and other side effects are commonly reported within the first week of beginning a ketogenic diet, especially if previously on a high-carbohydrate high-sugar diet. These side effect should not be alarming and are likely just your body's way of "detoxing" from your sugar addiction and adapting. After the first week on the ketogenic diet the negative effects usually subside and cravings for sugar and carbohydrates lessen. This is when blood sugar is becoming more regulated and the body is adapting. When I began the ketogenic diet I noticed many improvements such as cognitive benefits, energy increase, and no more mid-afternoon crash. Many others have reported the same thing. These improvements are usually reported to occur after the initial crash around weeks 2-3. As you get further along in the ketogenic diet the better you will feel due to the body's ability to adapt to the alternate fuel source. The duration of the ketogenic diet may range from 2-3 weeks minimum to 6-12 months maximum depending on the individuals health and goals (3).