You’ve heard of the keto diet. Everyone from Lebron James to the Kardashians has used the low-carbohydrate, high-fat diet for reasons like performance and weight loss.
The goal of the keto diet is to get the body producing ketones– a fundamentally different energy source than the carbohydrates and fats your cells typically use for energy. It can take several days of ketogenic eating before the body starts to produce ketones. And the time it takes to get into ketosis varies between individuals.
“Keto” comes from the word “ketogenic.” This is a nuanced term meaning that the body is producing ketones from fat.1 When blood ketone levels exceed 0.5mM, the body has achieved “ketosis.” So ketosis can be achieved either through diet or fasting (meaning the body is producing its own ketones to be ketogenic), or also by consuming products that raise blood ketone levels (like HVMN Ketone or ketone salts or MCT oils).
Limiting carb intake and protein intake encourages the body to burn fat–and thus produce ketones. Importantly, restricting proteins as well as carbohydrates limits the amount of substrate available for gluconeogenesis. This is the process of making glucose from non-glucose molecules such as lactate, glycerol, or protein.
Because the ketogenic diet is low-carbohydrate, it often gets confused with other low-carb diets out there. Just because a diet is low carb doesn’t mean it’s keto. It’s subtle differences in the macronutrients provided in the diet determine if the diet is ‘ketogenic.’
A macronutrient is something humans consume in large quantities to provide the bulk of energy to the body. The primary macronutrients are carbohydrates, fats, and proteins. For a diet to be ketogenic, it must be high in fat, low-moderate in protein, and very low in carbohydrates.
Here are some helpful definitions of diets with an element of reduced carbohydrate intake:
- The aim is to trigger the production of ketones in the body
- High fat, low/moderate protein, and low carbohydrate
Low-Calorie Ketogenic Diet
- The aim is to severely restrict calories to a level below the basic metabolic needs (i.e., <800 kCal)
- Even if this diet is relatively high in carbohydrates, the calorie deficit created can still lead to a state of ketosis
- Not sustainable long-term
- Defined in medical literature as a diet with < 30% energy from carbohydrates2
- May not lead to ketosis as the carbohydrate and protein intake could be too high
- This diet has several phases
- Initially, the aim is to restrict the carbohydrate intake to less than 20g per day. This degree of restriction is likely to lead to ketosis, although this is not an explicit aim
- Subsequently, the diet reintroduces carbohydrates to a level “the body can tolerate”3
- Less restriction on protein compared to a ‘true ketogenic diet–high fat, moderate protein, low carbohydrate.
- The aim is to limit the diet to foods that would have been available to Paleolithic man4
- Wide variability in interpretations
- Foods allowed include vegetables, fruits, nuts, roots, and meat
- Foods excluded include dairy, grains, sugar, legumes, processed oils, alcohol, and coffee
- No structured macronutrient target; however, following a Paleo diet results in higher protein and fat consumption than an average diet
Now you have a grasp of what makes the ketogenic diet unique–but where’d it start?
The History of the Ketogenic Diet
Fasting and Early Pioneers of the Ketogenic Diet
The concept of fasting (taking in zero calories) predates the ketogenic diet as we now understand it. Many of the benefits of fasting are likely due to the presence of ketones in the body.
Since the earliest days of man, fasting has been used as a tool to physically and spiritually cleansing.
The Bible describes fasting as a treatment for convulsions. The ancient Greek philosopher Hippocrates said, “To eat when you are sick is to fuel your sickness.”
Early advocates of fasting were obviously unaware of ketosis as a crucial factor in the anticonvulsant effect of fasting. In the early 1900s, physicians at the Mayo Clinic observed a link between a low-carb diet and fasting. They discovered that severely restricting dietary carbohydrates and increasing fat intake could decrease seizures in the same way as fasting.5 It was not until the mid-1900s, when scientists could measure ketones, that we understood fasting led to the presence of ketones in the body.
Epilepsy was not the only disease historically treated with a low-carbohydrate, high-fat diet. Low-carbohydrate diets were also advocated for patients with diabetes and obesity. Before the discovery of insulin in 1921, diabetes was managed through carbohydrate restriction. William Banting, an obese British mortician, popularized the weight loss benefits of a diet “stripped of starchy foods” in a pamphlet called “Letter on Corpulence, Addressed to the Public.”
The Dark Ages for the Ketogenic Diet
To many, a low-carbohydrate and high-fat diet is a counter-intuitive approach to support health. There is a widespread fear dietary fat is linked to obesity, high blood pressure, high cholesterol levels and other associated health complications.
In 1953 Ancel Keys, an American biochemist published an epidemiological study that introduced the “diet-heart” hypothesis. The study claimed dietary fat was a key risk factor in developing heart disease. The “diet-heart” hypothesis proposed blood LDL and cholesterol derived from dietary fat accelerates the development of atherosclerotic plaques.6
His work came at the time that US President Dwight Eisenhower, suffered a heart attack.
Following the advice of his physician, Eisenhower publicly cut back his fat intake. Nutrition was in the spotlight and Keys was able to further his hypothesis.
This led to radical changes in global food policy and public practice.
In 1977, the USDA Dietary Goals for Americans recommended a decrease in dietary fat intake, and a diet based on grains and cereals.7
At the time, there was still no clinical evidence supporting Keys’ “diet-heart” hypothesis. Subsequent large trials, including the Framingham Study and Women’s Health Initiative Randomized Controlled Dietary Modification Trial, failed to illustrate decreasing dietary fat lowered the risk of heart disease.8,9
Obesity rose following the adoption of the USDA guidelines. Some investigators hypothesized that increased dietary carbohydrates were responsible for the developing health crisis. John Yudkin, a British physiologist and nutritionist, described this phenomenon in his book “Pure, White and Deadly”10–the widespread fear of dietary fats caused scientists and nutritionists to overlook the role of sugar and starch.
Resurgence of ‘Low-Carbohydrate’ Diets
‘Low-fat’ dieting was widespread in the late 1900s. During this time, Dr. Robert Atkins became an infamous spokesperson for the keto diet. Dr. Atkins brought his version of the ketogenic diet to the masses in his 1972 book “Dr. Atkins’ Diet Revolution.” In his 40 years of practice, Dr. Atkins treated an estimated 60,000 patients for obesity and related conditions. At that time, there were no clinical studies to validate the benefits of the diet. Many patients reported side effects while starting the diet, including fatigue, weakness, dizziness, headache, and nausea. This uncomfortable induction phase was labeled the ‘Atkins Flu.’
After Atkins’ death in 2003, others started to promote the ketogenic diet for health. The Atkins Foundation recently funded a group of scientists to study the effects of the Atkins diet formally. This group of scientists includes Jeff Volek, Stephen Phinney, and Dr. Eric Westman. They discovered that the Atkins diet outperformed a diet based on the 1977 USDA guidelines with respect to measured coronary risk factors, including decreased low-density lipoprotein-cholesterol and total blood saturated FFA alongside increased high-density lipoprotein cholesterol.11 This outcome may be due to the decrease in carbohydrate and concomitant changes in the hormonal milieu, or due to effects of ketone bodies on substrate metabolism.
The pendulum of public perception begun to swing in favor of diets higher in fat, thanks to the emergence of influential writers and speakers such as Gary Taubes, Robert Lustig, and Nina Teicholtz, and clinicians and scientists such as Professor Tim Noakes, Dr. Jason Fung, and Professor Thomas Seyfried. The work of these individuals exposed flaws in the ‘diet-heart hypothesis.’
These influencers helped expose corruption in the political decisions that resulted in the last decades of vilification of dietary fat. Evidence illustrating the role of high dietary carbohydrate intake in the development of obesity and diabetes has started to grow. Much of the recent research suggests that low-fat diets may be harmful to health. This culminated with a recent meta-analysis of data from 18 countries, which linked increases in carbohydrate intake with increases in mortality.12
The fear of fat has continued to reverse. Over the last few years, the ketogenic diet has grown in popularity. Popular culture is starting to recognize and adopt the keto diet, and online searches have grown. More and more doctors now encourage and prescribe the ketogenic diet to treat metabolic disorders and obesity. Large online commmunities bring thousands of people together to discuss research, share keto diet before and after photos, and encourage each other.
Keto Diet for Weight Loss
The ketogenic diet can be used to help with weight loss and also to treat some diseases (discussed in detail elsewhere). Recently, the number of positive keto diet reviews has increased. The rising popularity of the diet has led to a demand for further randomized control trials to study its long-term efficacy. A key reason why the ketogenic diet helps weight loss is that it decreases hunger. This makes it easier to maintain a calorie deficit. It is important to stress that the overconsumption of calories will prevent weight loss, regardless of the macronutrient composition.
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