Diet Review - Ketogenic Diet
Finding yourself confused by the seemingly endless promotion of weight-loss strategies and anti-cancer diet plans? In this second article in my series on Diet Reviews, I take a look at the ketogentic diet.
Ketogenic Diet
The ketogenic or “keto” diet is a low-carbohydrate, fat-rich eating plan that has been used for centuries to treat specific medical conditions. In the 19th century, the ketogenic diet was commonly used to help control diabetes. In 1920 it was introduced as an effective treatment for epilepsy in children in whom medication was ineffective. The ketogenic diet has also been tested and used in closely monitored settings for cancer, diabetes, polycystic ovary syndrome, and Alzheimer’s disease.
However, this diet is gaining considerable attention as a potential weight-loss strategy due to the low-carb diet craze, which started in the 1970s with the Atkins diet (a very low-carbohydrate, high-protein diet, which was a commercial success and popularized low-carb diets to a new level). Today, other low-carb diets including the Paleo, South Beach, and Dukan diets are all high in protein but moderate in fat. In contrast, the ketogenic diet is distinctive for its exceptionally high-fat content, usually 70% to 80%, and with only a moderate intake of protein.
How It Works
For weight loss , the concept behind the ketogenic diet is that if you deprive the body of glucose—the main source of energy for all cells in the body, which is obtained by eating carbohydrate foods—an alternative fuel, called ketones is produced from stored fat (thus, the term “keto”-genic). The brain demands the most glucose in a steady supply, about 120 grams daily, because it cannot store glucose. During fasting, or when very little carbohydrate is eaten, the body first pulls stored glucose from the liver and temporarily breaks down muscle to release glucose. If this continues for 3-4 days and stored glucose is fully depleted, blood levels of a hormone called insulin decrease, and the body begins to use fat as its primary fuel. The liver produces ketone bodies from fat, which can be used in the absence of glucose.
When ketone bodies accumulate in the blood, this is called ketosis. Healthy individuals naturally experience mild ketosis during periods of fasting (e.g., sleeping overnight) and very strenuous exercise. Proponents of the ketogenic diet state that if the diet is carefully followed, blood levels of ketones should not reach a harmful level (known as “ketoacidosis”) as the brain will use ketones for fuel, and healthy individuals will typically produce enough insulin to prevent excessive ketones from forming. How soon ketosis happens and the number of ketone bodies that accumulate in the blood is variable from person to person and depends on factors such as body fat percentage and resting metabolic rate.
There is not one “standard” ketogenic diet with a specific ratio of macronutrients (carbohydrates, protein and fat). The ketogenic diet typically reduces total carbohydrate intake to less than 50 grams a day—less than the amount found in a medium plain bagel—and can be as low as 20 grams a day. For a 2000-calorie diet, this translates to about 165 grams fat, 40 grams carbohydrate, and 75 grams protein. The protein amount on the ketogenic diet is kept moderate in comparison with other low-carb high-protein diets, because eating too much protein can prevent ketosis. The amino acids in protein can be converted to glucose, so a ketogenic diet specifies enough protein to preserve lean body mass including muscle, but that will still cause ketosis.
Many versions of ketogenic diets exist, but all ban carb-rich foods. Some of these foods may be obvious: starches from both refined and whole grains like breads, cereals, pasta, rice, and cookies; potatoes, corn, and other starchy vegetables; and fruit juices. Some that may not be so obvious are beans, legumes, and most fruits. Most ketogenic plans allow foods high in saturated fat, such as fatty cuts of meat, processed meats, lard, and butter, as well as sources of unsaturated fats, such as nuts, seeds, avocados, plant oils, and oily fish. Depending on your source of information, ketogenic food lists may vary and even conflict.
The Research So Far
The ketogenic diet has been shown to produce beneficial metabolic changes in the short-term. Along with weight loss, health parameters that are associated with carrying excess weight may improve, such as insulin resistance, high blood pressure, elevated cholesterol and triglycerides. There is also growing interest in the use of low-carbohydrate diets, including the ketogenic diet, for type 2 diabetes. Several theories exist as to why the ketogenic diet promotes weight loss, though they have not been consistently shown in research:
A satiating effect with decreased food cravings due to the high-fat content of the diet.
A decrease in appetite-stimulating hormones, such as insulin and ghrelin, when eating restricted amounts of carbohydrate.
A direct hunger-reducing role of ketone bodies—the body’s main fuel source on the diet.
Increased calorie expenditure due to the metabolic effects of converting fat and protein to glucose.
In nearly all formal studies of the ketogentic diet however, calories were restricted to 800 - 900 kcal per day, which in-and-of itself would product weight loss regardless of the composition of the diet. So this casts some doubt on the validity of the ketogenic mechanisms for wieght loss touted by proponents of this diet. Of note also is that the drop-out rate for those involved in these studies was high overall due to the difficulty in following this diet.
Potential Pitfalls
Following a very high-fat diet is challenging to maintain and often leads to symptoms of extreme carbohydrate restriction that may last days to weeks. These include hunger, fatigue, low mood, irritability, constipation, headaches, bad breath and brain “fog.” Though these uncomfortable feelings may subside, staying satisfied with the limited variety of foods available and being restricted from otherwise enjoyable healthy foods like a crunchy apple or creamy sweet potato may present new challenges.
Some negative side effects of a long-term ketogenic diet have been noted, including increased risk of kidney stones and osteoporosis, and increased blood levels of uric acid (a risk factor for gout). Nutrient deficiencies may arise if a variety of recommended foods on the ketogenic diet are not included. It is important to not solely focus on eating high-fat foods, but to include a daily variety of the allowed meats, fish, vegetables, fruits, nuts, and seeds to ensure adequate intakes of fiber, B vitamins, and minerals (iron, magnesium, zinc)—nutrients typically found in foods like whole grains that are restricted from the diet. Other serious long term concerns with the ketogenic diet include (but are not limited to) muscle wasting, muscle fatigue, bone fractures, heart arrhythmias, and even death.
Is there any evidence that the keto diet can cure cancer?
No single food can cure cancer, but some research has shown a link between the keto diet and slowed growth of some types of tumors in mice. A few studies in humans with certain types of brain tumors have also shown promise. A very low-fat diet has been found to reduce risk of recurrence for certain types of breast cancer. While there’s the potential that the keto diet could help some cancer patients, it can also harm others. Depending on the type of cancer or cancer treatment, one's body may not be able to break down the proteins and fats. This could lead to signficant digestive problems.
Unanswered Questions
What are the long-term (one year or longer) effects of, and are there any safety issues related to, the ketogenic diet?
Do the diet’s health benefits extend to higher risk individuals with multiple health conditions and the elderly? For which disease conditions do the benefits of the diet outweigh the risks?
As fat is the primary energy source, is there a long-term impact on health from consuming different types of fats (saturated vs. unsaturated) included in a ketogenic diet?
Is the high fat, moderate protein intake on a ketogenic diet safe for disease conditions that interfere with normal protein and fat metabolism, such as kidney and liver diseases?
Is a ketogenic diet too restrictive for periods of rapid growth or requiring increased nutrients, such as during pregnancy, while breastfeeding, or during childhood/adolescent years?
Bottom Line
Available research on the ketogenic diet for weight loss and cancer treatment is still limited. Most of the studies so far have had a small number of participants, were short-term (12 weeks or less), and did not include control groups. A ketogenic diet has been shown to provide some short-term benefits in some people including weight loss and improvements in total cholesterol, blood sugar, and blood pressure. However, these effects after one year when compared with the effects of conventional weight loss diets are not significantly different.
Eliminating several food groups and the potential for very unpleasant and sometime very serous side effects may make compliance difficult. An emphasis on foods high in saturated fat also counters recommendations from the Dietary Guidelines for Americans and the American Heart Association and may have adverse effects on blood LDL cholesterol.
From my perspective, a ketogenic diet is not recommended due to the risks and questionable long term benefits. A modified carbohydrate diet following an anti-inflammatory eating pattern is much more likely to produce desired health benefits, weight reduction and cancer prevention. With that in mind however, I do recommend intermittent fasting as a method to induce beneficial short term ketosis which may lead to longer life and disease prevention.