I recently started a Ketogenic diet, and more recently, met someone who was thinking about starting one and asked me to explain how it works.
The ketogenic diet was invented over 100 years ago as a way of treating epilepsy. Oddly, people who adopted it also reported some interesting side effects, namely rapid weight loss and increased mental clarity. Along with these, a ketogenic diet has also been used to treat, prevent or reverse illnesses such as diabetes, heart disease, IBS/IBD and other digestive issues, Multiple Sclerosis, and autism, probably among many others. It's even been suggested to cure or prevent cancer, by cutting out the fuel source for cancer cells, sugar.
Here's what I wrote in response to my friend, much of it is summarized from presentations by Jason Fung:
Conventional diet wisdom says to lose weight, spend more calories than you consume, and to gain weight, reverse that. It's a big lie that many people believe. Eat less, and/or do more exercise, and you get preliminary results, but never long term, because your metabolism acts as a thermostat, always pushing toward the middle. Eat fewer calories, and your metabolism slows to preserve what energy you have left. Eat more calories and your metabolism speeds up to get rid of excess energy quickly. There have been studies done to show both effects.
It's not as simple as calories in, calories out, it also matters a lot where those calories come from.
Carbs are the easiest source to process, readily available, quick to convert to glucose. Carbs are stored in the body the way readily available, quick to consume food is stored in the fridge. People consume many carbs, and restock their "fridge" and their body spends those carbs as calories. Eat too many carbs, more than your "fridge" has capacity to hold, and your excess carbs get stored as fat in the freezer.
Most people never empty their fridge, they restock before supplies get low. Many people have excess supplies in the freezer. frozen, not as quickly accessible, takes some prep before being ready to eat. But if you decide not to restock the fridge, your body will turn to the freezer to turn fat cells into energy. Those fat cells may have even been from excess carbs. This process is called ketosis. There are no carbs from which to make glucose, so the liver starts producing ketones to convert fat to energy.
Slowly over time, your body eats itself, in the form of fat cells. This is called autophagy.
Dietary fat doesn't translate directly into bodily fat. What makes you fat is not the food you eat, but how your body responds to it. When your body consumes carbs, it produces more insulin. Insulin is like a traffic cop that directs incoming calories into either fat cells for storage or into energy production for immediate use. Too much insulin, and to some degree, cortisol and other hormones, is the reason for obesity, NOT caloric intake. Obesity/weight gain is a hormonal imbalance. Therefore, reduce carbs, in order to reduce insulin, in order to reduce weight. Dietary fat is more or less simply a caloric alternative to carbohydrates, but like bodily fat, will be processed by ketones produced by the liver.
Diabetes type 1 is when your body doesn't produce insulin, and type 2 is when your body resists the insulin in produces, so excess glucose spills over into your bloodstream.
Keto, and especially keto combined with intermittent fasting, are effective at treating, curing, or preventing Diabetes type 2, and maybe even helpful with type 1.
Intermittent fasting gives your digestive system a bit of rest and helps regulate insulin and metabolism to avoid spikes upward or downward.
To enter ketosis, it is recommended to begin with a "fat fast" which is essentially a carnivorous/zero carb diet. no vegetables or fruits, and obviously no grains and sugars for about 5 days.
Three common fat fasts are:
A dozen eggs a day only
30 strips of bacon a day only.
100g of beef and 3 Tbsp of butter per meal only
After 5 days, you're probably in ketosis. if you want to be sure, you can test your breath, blood or urine. After you are in ketosis, do whatever you can to stay there. if you drop out of ketosis, re-enter.
Ketosis is the defining aspect of a ketogenic diet. You can be in ketosis while observing any number of other dietary practices, including paleo and vegan, (obviously also including lacto-, ovi- or pescatarian) or while adhering to specific low carb diet protocols like Atkins, Weight Watchers, Banting, GAPS, and so on.
A good keto diet is about 75-80% fat, 15-20% protein, and under 5% carbohydrate. These are often called "macros" and some people think these percentages are the most important part of a diet, rather than counting calories for example.
for most people, 5% carbs is going to be about 20g net carbs. Net carbs = Total carbs - Fiber. Most above ground vegetables are carbs, but are high in fiber, so low in net carbs.
Basically, you can eat as much meat and salad as you want, combined with whichever fats and oils you like, but some are better than others. Coconut oil seems to be really good. I've seen one study where a group of men lost weight with only one change to their diet and no changes to their lifestyle, and that one change was to include two tablespoons of coconut oil daily (possibly as a replacement for another oil).
Eat as much as you want. but you won't want much. I'm full all day and into the next after just one meal. But if I get hungry later, I can eat again. People who do intermittent fasting try to stick to a rhythm of whatever ratio suits them best, 16:8, 18:6, 20:4, 23:1 (OMAD-One Meal a Day) or even every other day.
There are a few variations of keto, like lazy keto, where people don't want to be bothered tracking their macros, or dirty keto, where people still eat junk food/fast food, so long as they eat the right proportions of macros, and supposedly, high performance athletes might do a cyclical keto diet, keto on the weekdays and carb loading on the weekends, though I don't see the point of dropping in and out of ketosis every week.
Mostly, my one meal a day this past week has consisted most days of 3 eggs, 3 strips of bacon, fried in butter and coconut oil, topped with avocado, salt, pepper, and cheese and black olives on the side, with an occasional salmon patty and some shrimp with herb butter. As I said, it's very filling and it's enough to get me through the day on just one meal. However, now that I am in ketosis, I can start adding vegetables back in.
In regards to keto, Stephen Phinney is one of the most knowledgeable researchers, and possibly has the longest career studying ketones and the effects of eating ketogenically of anyone still alive. In this video series, he gives an excellent overview of what it is, and how it works.
I have some experience in diets that inadvertently wound up with me in ketosis. I was working with my parents at their print shop and book bindery, and we ate all our meals together, so when they started Somersizing (a Suzanne Somers-sponsored diet regimen that essentially focused on controlling blood sugar levels by separating fats and proteins from carbs), and when I started skipping the carb and starch portions of the diet in favour of salads and high-fat dressings, I wound up dropping weight to unhealthy levels (I went from a pretty stable 220-230 lbs to 175 lbs, and I am just over 6'), and because I didn't understand what my body was doing, I didn't know that I could have fixed things by eating more fat. I just went back to incorporating some carbs, which kicked me out of ketosis.
I am going to have to take a look at the ketogenic diet and how to meal plan around it. We already love avocados, and I crave fatty meat like a forced-vegan kitty cat.
A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects.
-Robert A. Heinlein