My Notes on Ketosis and Intermittent Fasting



-doesn’t change what you eat, it changes when you eat.

-Diets are easy in the contemplation, difficult in the execution. Intermittent fasting is just the opposite — it’s difficult in the contemplation but easy in the execution.

-I skip breakfast each day and eat two meals, the first around 1pm and the second around 7pm. Then, I fast for 16 hours until I start eating again the next day at 1pm.

FED STATE:Your body is in the fed state when it is digesting and absorbing food. Typically, the fed state starts when you begin eating and lasts for three to five hours as your body digests and absorbs the food you just ate.

FASTED STATE:Your body isn’t processing a meal. The post–absorptive state lasts until 8 to 12 hours after your last meal, which is when you enter the fasted state. It is much easier for you body to burn fat in the fasted state because your insulin levels are low.

Because we don’t enter the fasted state until 12 hours after our last meal, it’s rare that our bodies are in this fat burning state. This is one of the reasons why many people who start intermittent fasting will lose fat without changing what they eat, how much they eat, or how often they exercise. Fasting puts your body in a fat burning state that you rarely make it to during a normal eating schedule.

Intermittent fasting activates many of the same mechanisms for extending life as calorie restriction. You get the benefits of a longer life without the hassle of starving.

DAILY INTERMITTENT FASTING Most of the time, I follow the Leangains model of intermittent fasting, which uses a 16–hour fast followed by an 8–hour eating period. This model of daily intermittent fasting was popularized by Martin Berkhan of, which is where the name originated. It doesn’t matter when you start your 8–hour eating period. You can start at 8am and stop at 4pm. Or you start at 2pm and stop at 10pm. Do whatever works for you. I tend to find that eating around 1pm and 8pm works well because those times allow me to eat lunch and dinner with friends and family. Breakfast is typically a meal that I eat on my own, so skipping it isn’t a big deal.

LEANGAINS DAILY INTERMITTENT FASTING Because daily intermittent fasting is done every day it becomes very easy to get into the habit of eating on this schedule. Right now, you’re probably eating around the same time every day without thinking about it. Well, with daily intermittent fasting it’s the same thing, you just learn to not eat at certain times, which is remarkably easy. One potential disadvantage of this schedule is that because you typically cut out a meal or two out of your day, it becomes more difficult to get the same number of calories in during the week. Put simply, it’s tough to teach yourself to eat bigger meals on a consistent basis. The result is that many people who try this style of intermittent fasting end up losing weight. That can be a good thing or a bad thing, depending on your goals. This is probably a good time to mention that while I have practiced intermittent fasting consistently for the last year, I’m not fanatical about my diet. I work on building healthy habits that guide my behavior 90% of the time, so that I can do whatever I feel like during the other 10%. If I come over to your house to watch the football game and we order pizza at 11pm, guess what? I don’t care that it’s outside my feeding period, I’m eating it.

WEEKLY INTERMITTENT FASTING One of the best ways to get started with intermittent fasting is to do it once per week or once per month. In this example, lunch on Monday is your last meal of the day. You then fast until lunch on Tuesday. This schedule has the advantage of allowing you to eat everyday of the week while still reaping the benefits of fasting for 24 hours. It’s also less likely that you’ll lose weight because you are only cutting out two meals per week. So, if you’re looking to bulk up or keep weight on, then this is a great option. Long day of travel or the day after a big holiday feast are often great times to throw in a 24–hour fast.

ON EATING MORE MEALS: Your body burns calories when it’s processing food. So the thought behind the more meals strategy was that if you ate more frequently, you would also burn more calories throughout the day. Thus, eating more meals should help you lose weight. Here’s the problem: The amount of calories you burn is proportional to the size of the meal your body is processing. So, digesting six smaller meals that add up to 2000 calories burns the same amount of energy as processing two large meals of 1000 calories each. It doesn’t matter if you get your calories in 10 meals or in 1 meal, you’ll end up in the same place.


Ketogenic diets emphasize natural fats and protein (meat, fish, poultry) and restrict foods high in carbohydrate (sugars and starches). Ketosis is an energy state that your body uses to provide an alternative fuel when glucose availability is low. It happens to all humans when fasting or when carbohydrate intake is lowered.

Ketogenic diets are not high protein diets, as the majority of calories come from natural fats. Protein intake is moderate and only small amounts of carbohydrates are allowed. Because fat is so dense in calories, this just means adding a moderate amount of extra butter, olive oil or other natural fat to fresh, whole food meals.

The restriction of carbohydrate is the key health factor in this diet. When carbohydrate foods (sugar and starch) are digested, they are broken down into blood sugar (glucose) in the body. The more carbs we eat, the more glucose is created. If we reduce carb intake and instead eat more fat and protein, it causes our internal metabolic pathways to switch from burning sugar to burning fat.

This switch produces ketone bodies while at the same time reducing blood sugar and insulin levels. As blood glucose and insulin levels drop and ketone body levels rise, the heart, muscle and brain reduce glucose usage and instead rely on fats and ketones to fuel themselves. This state of “nutritional ketosis” is beneficial, and in fact, ketone producing diets are much more powerful than most people realize.

  • Body Fuel Basics *

The first cellular fuel is GLUCOSE , which is commonly known as blood sugar. Glucose is a product of the starches and sugars (carbohydrates) in our diet. This fuel system is necessary, but it has a limitation. The human body can only store about 1000-1600 calories this way. The amounts stored depend on how much muscle mass is available. Men will be able to store more because they have larger muscles. Since most people use up about 2000 calories a day just being and doing normal stuff, you can see that if food weren’t available for more than a day, the body would run out of energy. Not good for continuing life.

The second type of CELLULAR FUEL are ketone bodies, which come from the breakdown of fatty acids. These come from fats we eat or from the metabolism of stored fat from our fat cells. The human body can store hundreds of thousands of calories in the form of fat, so we could say that this system of energy is almost unlimited, depending on how long one goes without food. Eventually, it would get used up, but people have been known to fast for months and live through it.

When glucose levels are low, especially over time, most cells will switch to using ketone bodies for fuel. Ketones allow cells to be metabolically flexible, so to speak. Even the brain and nerve cells, which are heavily dependent on glucose can utilize ketone bodies for fuel. This ability of most normal cells to use ketones when glucose is unavailable indicates that their cellular mitochondria are healthy and functioning properly.

In addition, ketones have some unique properties which make them a “cleaner” fuel for your cells to use. Burning fat for fuel causes less oxidative damage (think “free radicals”) to the cell, and actually makes it possible for the cell to create much more energy than it can from glucose.

Ketosis and Ketones To the Rescue So how does our body make ketones out of the stored fat? When stored fat (in the form of triglyceride) is called upon to be metabolized for fuel, a substance called hormone sensitive lipase (HSL) breaks the triglyceride compound down into one glycerol molecule and 3 fatty acid molecules. These fatty acid molecules come in various lengths of carbon based chains.

The fatty acids then flow into either liver or muscle cells and are transported into the mitochondria of the cell to be metabolized carbon by carbon in a process called beta-oxidation. As glucose levels fall and fatty acid levels in the blood rise, the liver cells ramp up beta-oxidation which increases the amounts of a molecule called Acetyl-CoA. As the level of Acetyl-CoA rises, it is shunted to a process called ketogenesis. Ketogenesis generates a ketone body called acetoacetate first, and this ketone is then converted into the two other types of ketones: beta-hydroxybutyrate, and acetone. Meanwhile, the glycerol part of the fat molecule gets converted into glucose in a process called gluconeogenesis, which means “make new sugar”.

Ketosis takes a few weeks for the body to become “keto-adapted*” and switch to burning ketones for fuel once carbohydrate consumption is lowered. Carbohydrate intake levels have to be lowered enough (below 60 grams per day or lower depending on insulin resistance levels) for ketone bodies to be made at a level that the brain can use. If you only lower carbohydrate intake a little, then the ketotic process gets short circuited, and can’t do its job of taking over as a fuel source.

AS KETONES LEVELS RISE IN THE BODY, THE CELLS OF HEART, BRAIN AND MUSCLES CAN USE THEM FOR FUEL. And once the body is using ketones as a main fuel source, there are some profound and positive health effects. Ketogenic diets are very effective for correcting cellular metabolic dysfunction. The high blood sugar of diabetes gets reversed, the seizures of epilepsy can be calmed, Alzheimers and Parkinsons symptoms are alleviated, extra weight can be lost, joint pain is diminished and so on. In other words, the ketogenic diet is not a “fad.” It is a potent regulator of metabolic derangement, and when formulated and implemented correctly, it can be extremely effective at reversing all kinds of health problems.

Although ketones are beneficial, the body must still have some glucose, mostly for the brain and red blood cells. If a person goes without food for a long period of time, the body will breakdown fat and muscle to create glucose for the brain, because without some glucose, the brain will die and take you with it.

This brain glucose need is the main reason that registered dietitians insist on keeping alive the myth that carbohydrates are essential nutrients (meaning we have to eat them or we will die). This is incorrect, biochemically speaking. RDs teaching that carbs are essential neglect to take into account that the brain can use ketones for over half of its fuel requirements once carbohydrate intake is lowered and ketone production ramps up. The process of gluconeogenesis can make all the glucose the brain needs, once the body is keto-adapted (good at burning ketones for fuel). So although glucose is essential for the brain, eating carbohydrates to make glucose is NOT essential, especially if you are in ketosis.

Normal nutritional ketosis is NOT dangerous. Every person alive goes into mild ketosis each time they go without eating for 6-8 hours. The effects of ketosis vary with individual experience but ketones in normal amounts are not dangerous.

Unless you are a Type 1 diabetic (meaning your pancreas makes no insulin at all) or a Type 2 diabetic with a really burned out pancreas, ketosis is kept in check by the presence of insulin in the body. Insulin regulates the flow of fatty acids from our fat cells. As long as insulin is circulating within the body, in general, the flow of fatty acids and the production of ketone bodies is highly regulated and limited to a range that is not dangerous.

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