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Insulin – Fat – Hunger

What They Are and How They Interact – Based On Good Calories, Bad Calories by Gary Taubes

Have you ever wondered:

• Why you’ve gained weight?
• Why you get hungry at night?
• How to sort between all the conflicting the dietary advice you get?
• Is there a dietary approach that makes sense?

It turns out that insulin is a key hormone that determines not only what you eat but also how much. As you keep reading you’ll see how insulin determines the foods that you crave and makes you eat much more than your body needs.

A year ago I read Good Calories, Bad Calories by Gary Taubes. I found the book absorbing and mind blowing. It gave a theory of everything (food related). And it made a lot of sense. I read the book and things just clicked.

But the book was also dense, which is why Mr. Taubes later put out a simplified version as well (titled Why We Get Fat). While I felt the ideas were compelling, I felt that I didn’t fully grasp how they all meshed together. I could see the trees, but not the forest.

I recently read the book again. After considerable reflection, I feel that a key part of the book is his explanation of insulin. A deep understanding of insulin fundamentally changed how I see and understand food, diet and health. This view of insulin was paradigm shifting and possessing extraordinary explanatory power. It explains why we get hungry, what makes us feel satisfied, why we gain weight, why we lose weight, the impact of carbs and much more.

In the discussion below, I’ve taken many ideas Mr. Taubes mentions in passing and organized them into a clear and rigorous structure. I’ve also added my own insights and reflections. If there is sufficient interested, I will add detailed references. It is my hope that Mr. Taubes will look over this outline and if he does I would love to post his response. Any errors are of course my own. Enjoy!

Assumptions (axioms):

• The body requires a stable, constant source of energy – if we only got only energy when we ate, we’d need to eat constantly or we’d run out of energy.
• Meals provide more energy than the body’s immediate needs – since we are not eating 24/7, it must be that we take in more energy during meals than we need and utilize that energy when we’re not eating (in between meals)
• The body requires a signaling mechanism to know when to store energy and when to utilize the stored energy – it needs something to tell it during meals, “you’re taking in extra energy right now, store it. Once stored, you can utilize this energy between meals and when you sleep at night.”
• The body needs a signal to eat the right amount during meals – if we constantly ate too much during meals, we’d need to store the energy as fat. We need a satiety signal.
• Most people have a set weight – even obese people settle on a certain weight. If they fast and then return to the same diet, eventually their weight returns to this set point.
• Evidence seems to point to insulin being the key driver of the above energy mechanisms

How Insulin Stores Energy, Allowing Us To Eat Meals Instead of Grazing

(Note – The terms energy and fuel will be used interchangeably)

• When you eat, your body converts food into energy. Some of the energy is utilized immediately. Most is stored as fat. How does the body know how much to store as fat?
  • When we eat the body produces insulin. Insulin regulates energy production in fat cells. The presence of insulin signals the fat cells to stop producing fuel and start storing. It also tells the fat cells to start absorbing fuel from the bloodstream
  • This relationship (between insulin and fat cells) drives hunger…
• Increased insulin levels make us hungry
  • Insulin production instructs the body (in its fat cells) to store available energy as fat. Since the available energy has been stored, the body feels a need for nourishment. This need for nourishment is felt as hunger. 
  • We see insulin producing hunger with mice – when mice are given insulin injections, they eat. If given the injections when sleeping, they will wake up and eat.
    • This is because the insulin stops the mice from accessing their energy reserves. Essentially insulin makes them starve.
• It follows that if we produce higher levels of insulin when eating, then we will store more food energy as fat. We will be hungrier and eat more.
  • Conversely, if our body produces less insulin during a meal, then more of the food energy is available for use. Since the body has more energy available it will eat less. The lower insulin level will result in less food eaten and less fat storage.
• We need to determine what causes higher insulin production during meals. How do higher insulin levels affect the body and energy production?
  • If insulin makes us store fat during meals, thus preventing the food energy from being utilized, thus increasing hunger, wouldn’t this cycle cause us to eat ad infinitum?

Insulin – How Pregnant Women Gain Weight

• There is always insulin in the body. Sometimes there is more (during meals), sometimes there is less (between meals).
• The body has different fat cells which are more or less insulin sensitive. Under the influence of a set amount of insulin and a set amount of food energy, certain cells will store food energy (get fatter), other cells will not. This results in us being fatter in certain parts of our body and leaner in others.
• This is why men tend to develop fat around their midsection while women tend to develop fat in their breasts and buttocks. Pregnant women gain weight (and are at increased risk of gestational diabetes) due to increased insulin levels.
  • Example – case of a women who a skin graft from her buttocks onto her hand. The skin graft portion got very fat compared to the rest of her hand and had to be removed.
• Insulin sensitivity is dependent on many factors including hormones. When men are younger, testosterone tends to make them leaner. As testosterone levels decrease with age, men tend to gain weight.
  • Women gain weight upon the hormonal effects of puberty and pregnancy. Estrogen tends to prevent women adding significant stomach fat until its levels lower in mid-life. 
• Just like cells very in their insulin sensitivity, so do people. Some bodies tend to be more sensitive to insulin, some less. The same meal can result in one person losing weight and second person gaining.
  • At the same time, all other things being equal, higher insulin levels during a meal will result in a person storing fat
    • Higher insulin levels between meals will also result in hunger
• Paradoxically, while insulin causes us to store energy in fat cells. Obesity is caused by insulin resistance. As we will see…

Insulin – A Continuum

• When insulin levels rise, the body stores energy as fat. When levels fall, the fat cells release energy for use.
• Fat cells have storage for energy. Sometimes they are more filled and get larger. Sometimes they are less filled and get smaller.
• Imagine that it is at a time between meals and your insulin levels are low. The fat cells will release energy up to a point. Once they are relatively depleted of energy, the presence of insulin in the body will cause them to stop releasing energy. This is when you will start getting hungry.
• Review – in between meals fat cells release energy. At some point they stop releasing energy and we get hungry again. It’s time for the next meal.
• We know from long-term fasting (anecdotally, I’ve water fasted for 15 days) that the fat cells have a huge energy surplus to release. Why in a non-faster, do the cells stop releasing energy when it’s time for the next meal?
• It must be that the non-faster has significant amount of insulin in the body even between meals. As the cells expend and reduce their energy reserves, they become more sensitive this insulin and stop releasing energy.
• This explains why the first two days of a water fast are the most difficult and there are extreme cravings (often for very high carb foods).
  • When we begin a fast, insulin levels are initially at their elevated non-fasting levels. This insulin stops the cells from releasing energy. The body is energy starved and therefore intensely hungry. It is insulin that causes the intense cravings.
  • As the body adjusts to the fast, insulin levels slowly reduce. The fat cells can release their energy which is as I’ve personally experienced, adequate for at least 15 days.
  • As we’ll see, this explains why it takes a few days for significant ketosis to start and why it’s important to have fatty meat on a keto diet. Too much protein (for example, lean cuts of meat) will prevent the body from utilizing its fat stores.

What Makes Us Satisfied After A Meal?

• When we don’t eat, we are in a state of fasting. How do we get energy?      
  • The fat cells release their stored energy into the body
• But how do the fat cells know how much energy to release into the body?
• This is based on two factors:
  • Levels of insulin
    • Lower levels of insulin in the body result in (allow) the fat cells to release energy. In between meals, insulin levels lessen.
  • A type of insulin resistance
    • Absorbed too much food energy – when insulin has pushed a large amount of food energy into the fat cells, instead of being receptive to more energy, they become predisposed towards expelling energy (even if insulin levels remain high), additionally:
    • When insulin has remains high for a substantial period of time, the fat cells become somewhat resistant to it. Even though the elevated insulin is signaling for them to store food energy, the cells become resistant to the insulin, and will begin expelling energy
      • Thus when a meal begins and insulin rises, the fat cells are sensitive to the insulin and absorb food energy. As the meal continues, they begin to ignore the insulin signal, stop storing energy and begin expelling (providing) energy to the body (this would be acute insulin resistance). We feel satisfied.
      • (This is also how diabetics and others with insulin resistance are able to get energy. Without insulin resistance, these diabetics would keep eating and storing away the fat until they became gargantuan. Instead their cells become resistant to insulin, thereby allowing them to expel energy and supply it to the body. Unfortunately, then health problems develop because now blood sugar (energy levels) rise. The body then compensates by raising insulin levels and in time the cells become further resistant.)
• To summarize: as a meal progresses and fat cells become filled with energy and insulin levels decrease. Additionally, the cells start to ignore the insulin signaling which frees them to begin supplying the body with energy. Then we feel satiated and stop eating.

Why We Like Carbs, Especially Sweets, And Why They Raise Insulin Levels

• For millions of years, our evolutionary environment contained two types of food:
  • Animal food – containing protein and fat
  • Proto-Plant food – our ancestors did not have the domesticated plants we had today. They had wild, uncultivated plants, such as tubers. Our domesticated plants are bred for easy digestibility. They are sweeter, higher in carbs and are digested into energy more rapidly. Our plants are not the proto-plants of our ancestors.
• During a meal, the protein and proto-plants were slowly digested and converted into energy. As blood sugar slowly rose during meals, insulin would also rise. Since this rise in insulin occurred slowly and gradually, the degree of hunger produced by this insulin was appropriate. Since the body was more insulin sensitive, less insulin was needed in order store extra energy as fat. Insulin remained at constant, relatively low levels.
• Domesticating wheat, sugar and other carbs resulted in a vastly different insulin equation.
• When eating wheat, carbs and especially sugar, the energy is digested quickly. The body is then filled with an overabundance of energy. Blood sugar rises rapidly and insulin levels must spike in order to store this excess sugar as fat.
• But then immediately afterwards, insulin levels would crash. Here is why:
• With animal protein and proto-plants, blood sugar would rise slowly and insulin levels would correspondingly rise slowly. Since digestion occurs slowly, the insulin levels would remain slightly elevated until digestion finished. As digestion and incoming energy slowed, insulin levels would slowly go down.
• But with carbs and sugar, digestion is very different. These foods enter the bloodstream very rapidly, so insulin levels must rise quickly and intensely in order to keep up. But since carbs are digested quickly, the fat is quickly stored, but insulin levels remain elevated.
  • Now the carbs are digested and the elevated insulin is telling the fat to store energy. The elevated insulin is effectively starving the body. We are ravenous and want to eat more. Carbs with their immediate digestibility (conversion to energy) are the most appealing
• Carbs make us hungry. They make us eat more (especially more carbs).
  • When we eat carbs, we keep eating until the fat cells become engorged and stop accepting more energy or the cells ignore the insulin (acute insulin resistance).
• This is how carbs make us fat:
  • We eat too much and we store what we eat
• This is how carbs cause diabetes:
  • Carbs cause chronically elevated insulin levels. This forces the cells to stop listening to insulin. While at first this insulin resistance is acute (short-term), eventually it becomes chronic (long term).
  • The cells ignore the insulin signaling and blood sugar rises. At prolonged high levels, blood sugar becomes dangerous. One example is that diabetics will loss sensation in their limbs and then the limbs themselves. Once someone has blood sugar over two hundred they begin to develop health problems. At over 300 or 400 it is often advised to call EMS. I worked with a diabetic who got a reading of over 700.
  • At the same time, the body tries to lower the blood sugar levels by raising insulin production. Chronically elevated insulin is dangerous. It also makes us eat more, both during and between meals. The cells then begin to ignore the higher levels of insulin. They become more insulin resistant and the cycle continues.
• This is why carbs make us snack between meals and late at night – typically, insulin levels would recede between meals and during the nighttime fast. Carbs can elevate insulin even between meals. This results in a cycle of, hunger throughout the day, eating throughout the day and higher insulin levels throughout the day.
• This could explain why eating at night causes an elevated insulin response – Multiple studies argue that eating at night causes the body to produce more insulin. But perhaps it’s not the act of eating at late hours that causes the insulin response. An alternative is that snacking at late hours is caused by insulin induced hunger. This elevated insulin occurs side by side with insulin resistance. When someone with insulin resistance eats, they will produce elevated insulin to overcome the resistance.
• This partially explains why we gain weight as we age – with age and years of eating carbohydrates, the bodies insulin response changes. We develop metabolic problems and we start to gain weight. 

Why Carb Cravings?

• Since insulin deprives the body of energy (by shoving into the fat cells), the body is starving
• Eating protein or fat will give the body energy after a slow digestion process. It will not feed the body now.
• Carbs and especially sweets will digest rapidly and provide instant energy. From a hungry low, you’ll go to a sugared up, energized high.
• Of course, to deal with this excess sugar energy, the body will need to produce more insulin
• The elevated insulin will shove this sugar energy into the fat cells. Soon you will be hungry again and crave a carb fix.
• This provides a conceptual background to my approach to carb cravings – when I feel a carb craving, I try to eat ketogenic foods (for example very buttered eggs or ground beef) to and beyond satiation. I find that the carb cravings will disappear. Sometimes I will also feel very tired afterwards.
  • If carb cravings are produced by elevated insulin, ketogenic foods will provide energy to the cells and keep insulin low. These foods won’t provide an instant fix like carbs, but they eliminate the cravings.
  • This explains why when starting the carnivore diet, it’s advised to eat until satiation and that if you don’t, you’ll break the diet.
    • When going off a high carb diet there will be elevated insulin levels. The insulin instructs the fat cells to hold onto their energy. The body is starving for fuel. It will crave carbs. But only by eating ketogenic foods will insulin levels and cravings slowly subside.
  • Many describe how after a few weeks on the carnivore diet the carb cravings disappear

Why Those On Carnivore and Keto Diets Eat Less Frequently

• Many people on the carnivore diet (fatty meat diet) describe that they naturally transition to eating twice a day or once a day
• On the keto diet, people seem to eat less frequently. Many on the keto and slow-carb diets also practice intermittent fasting (eating less meals). As we just saw, intermittent fasting happens naturally in the carnivore diet.
• The keto diet can be described as low-carb, the carnivore diet can be described as super low-carb or zero-carb.
• When eating a carnivore diet, insulin levels will rise slightly during and after the meal as the protein is slowly digested into sugar. A small rise in insulin will direct the slight and extended excess of energy into the fat cells.
  • When the meal is done, insulin levels are very low and fat cells can easily expel energy. Low insulin results in a continuous and adequate supply of energy. With adequate energy the body is not hungry.
• This explains how many on the carnivore diet have described how easy it is for them to skip even their low-frequency meals if needed
  • While their mouths say, “I control the food instead of the food controlling me”, their body says, “your insulin is low, so your fat cells are providing you with lots of energy.”

Why Smells, Artificial Sweeteners and Dairy Make You Hungry

• The body produces insulin in order to reduce over-elevated blood sugar (energy) levels. If it only started producing insulin once blood sugar became elevated, it would be too late. Therefore there is an initial wave of insulin when anticipating the food.
• This way the body is prepared for the anticipated rise in blood sugar. There is a second wave of insulin that occurs much later when we digest the food. This wave is more titrated (measured) according to the energy entering the body.
• Scientists have measured insulin levels rising from tasting sweetness, smelling food and even thinking about food.
  • When rats were given a signal that food was coming[i] their insulin levels rose.
• Scientists were able to determine people cravings based on how much their insulin rose based on delicious aromas
  • People who got more intense cravings from food aromas also produced more insulin when yummy food
  • This insulin response also happens when seeing or even thinking about appetizing food
• This explains you pass by a pizza store, you smell the delicious pizza and you become hungry. A customer is born.
  • Scientists also noted that when we feel full, our cravings (and insulin response) to smelling food is reduced
• It’s possible that carbs taste good because of insulin cravings. Just like a cigarette creates a craving to smoke, carbs create a craving to eat carbs.
• This could explain why zero calorie sweeteners could have an effect on weight and hormones. The body tastes the sweetness and produces insulin. Just like sugar will produce insulin, saccharin, aspartame and other sweeteners could theoretically produce increased insulin, hunger and fat accumulation.
• This can also explain why some people on the carnivore diet will sometimes abstain from heavy cream.
  • Gary Taubes describes how he cut heavy cream from his coffee (his only dietary change) and lost 20 pounds.
  • In theory heavy cream contains only fat with close to zero carbs and zero protein. It should be ketogenic and should not produce insulin.
  • Gary Taubes describes that for some, dairy paradoxically produces an insulin response.
  • Milk seems to produce a higher glycemic index response then you’d think based on the sugar contents
  • When a cow makes milk, it is so that the baby cow can grow and bulk up. Perhaps dairy is engineered so that it triggers insulin even when absent sugar.
  • Heavy cream does have a sweet taste, so it might trigger an insulin response, just like an aroma
  • I’ve noticed that when eating only dairy, my blood sugar gets lower (the next morning glucose read has produced some of my lowest readings). Perhaps there is a difference between eating dairy alone (like baby humans and cows do) and combining it with other foods.
• This explains why once I decide to break my fast, I get intense food cravings
  • My body is anticipating food and ramping up insulin
  • The cravings are very intense when I anticipate breaking the fast on carbs. When I commit to breaking the fast on ground beef, the cravings are much lower. (The cravings are also much lower during the fast. (Somehow it’s much easier to fantasize about ice cream and pizza than about ground beef.)
• Similarly, during the coronavirus I made a grocery order. The only pickup window was the next day. I decided to treat myself to some ice cream. Right away (the day before), I started getting intense carb cravings. In the end, the store was out of ice cream. It was easy to skip bread and stay in a ketogenic diet. 

Why Too Much Protein Prevents One Entering Ketosis

• Gary Taubes argues that carbs hijack the insulin response intended for digesting protein
• Protein slowly breaks down into blood sugar and insulin helps the body store excess energy (blood sugar) so we can use it between meals
  • Carbs cause rapid rise in insulin leading to an insulin roller coaster which results in excess eating and diabetes and other diseases of civilization
• It follows that when a low carb diet includes too much protein, the resulting protein breakdown into sugar will result in slightly elevated insulin levels. This tells the fat cells to hold onto their energy.
• You can’t enter ketosis without significant utilization of fat stores.
  • Eating fattier cuts of meat results in two things:
    • Eating less protein (since if you’re eating more fat, you’ll be eating less protein, assuming your total food volume stays the same)
    • The fat buffers the protein. This is why ice cream is (relatively) low on the glycemic index because the fat slows down sugar digestion and breakdown. Fat will also buffer protein, making it breakdown slower, thus reducing the insulin response and allowing increased utilization of fat cells.  

Why Excercising Helps Diabetics and Speeds Up Entry Into Ketosis

• Exercised is prescribed to help diabetics lower their blood sugar. How does it work?
• Tim Ferris describes how entering ketosis (intense fat burning) quickly during a fast makes fasting much easier. He recommends speeding up entering into ketosis by going on a four hour walk. How would a walk speed up entry into ketosis?
• Insulin tells the body to store the blood stream energy as fat. It stands to reason that exercise would do the opposite.
  • Exercise will tell the body it needs energy and to utilize its energy stores. It could do this either by lowering insulin or by sending a hormonal signal opposing the insulin signal
  • I’ve noticed that exercising will reduce hunger levels (as will very hot baths)
  • If I’m fasting and feeling very hungry, a hot bath will usually cause the hunger cravings to subside
• When exercise instructs the body to utilize the energy stored in fat cells, it is effectively instructing the body to accelerate its entry into ketosis. (I’ve entered my deepest state measured state of ketosis after exercising during an extended fast.)

Insulin Explains the Initial Fasting Phenomena

• For the first two days of a fast, you feel ravenous. There are intense cravings, especially for carbs. Then the cravings go away. People describe themselves during the later stages of a fast as feelings energized and high[ii].  
  • Tim Ferris recommends eating a low carb meal before fasting.
  • The initial stage of fasting is much easier for those on a keto and especially carnivore diet.
• This can be explained by the initial higher insulin levels which decrease during a fast
• Even between meals, we have insulin flowing through the body. In spite of this insulin, our engorged and insulin resistant fat cells expel food. At some point the tide turns and the insulin causes our cells to stop exporting fuel. We get hungry.
  • (See above, “What Makes Us Satisfied After a Meal)
• For the first two days of fasting, our insulin levels remain elevated. The insulin increasingly locks the energy in our cells and our body is literally starving. We develop cravings, especially for carbs. (See above, “Why Carb Cravings?”)
• As the fast progresses, the insulin levels gradually decline and cells start releasing energy. The hunger recedes.
• Without cravings, we feel satisfied, even high. 
• This explains how low carb diets (and even meals) can make the beginning of the fast easier. Low carb eating results in lower insulin levels. In the initial stages of a fast, this translates into less cravings, more energy and quicker entry into ketosis (intense fat burning).

Insulin Explains Why You Get Carb Cravings When Breaking a Fast

• I’ve found that when I finish a fast I will get intense carb cravings. It’s so intense that initially I would eat till I got a stomach ache. I recall one time breaking the fast with watermelon juice, my energy and state of mind was amazing. Two hours later, I started eating and eating and eating (carbs). The state of hunger and ravenous appetite would go on for days.
• I recall forcing myself to make an end of fast food plan to limit consumption. It was very hard to stick too.
• Then I discovered ground beef. If I ate fatty ground beef at the end of a fast (despite the carb cravings), I would eat in moderation. I would feel the rush of energy, I would feel amazing, but I would not overeat.
• What explains this phenomena?
• Peter Attia has said that if one eats carbs after a fast, the body overproduces insulin. That makes sense because for someone who eats a typically high carb diet:
• In a fed state, insulin levels will be somewhat elevated, even between meals.
• This means that when eating, the insulin in the system will work together with the food insulin response to store the excess energy
  • But when fasting, insulin levels get very low (see above – Insulin Explains Initial Fasting Phenomena)
  • If you eat carbs, they are digested rapidly. Blood sugar (energy) is too high and there is no insulin to instruct storing the excess energy.
  • In response to the high blood sugar there will be an insulin spike.
• When breaking a fast on carbs, there is a blood sugar spike which can be felt as an intense high. Then to compensate for the excess blood sugar, there is an insulin spike. With insulin rising to higher than normal levels the body stores all circulating energy as fat. Without energy, you are starving, ravenous.
  • This intense cycle of hunger followed by gluttony followed hunger… can go on for days
  • It stops once the fat cells start to get filled up with energy and to become insulin resistant (see above: What Makes Us Satisfied After a Meal)
  • At this point the insulin roller coaster starts to moderate. We can feel satiation again.
• However, when eating fatty ground beef, insulin levels rise in a very slow, moderate way due to the slow and gradual breakdown of fat-buffered protein
  • The body gets nourishment after the fast without the insulin roller coaster
  • Additionally, when insulin levels are even semi-elevated, the insulin signals to store a lot of the food we’re consuming. When breaking a fast with ground beef, insulin levels stay very low. All that food energy becomes available.
    • This explains the wonderful energy and high (which is absent any low) that accompanies breaking a fast with ground beef.

Why Do People Tend to Have a Set Weight

• We all have a baseline or set weight. Even the obese don’t put on weight forever. They reach a certain weight and will stay there for years. Why?
• Insulin correlates with weight. The fatter someone is, the greater their insulin levels. Increased insulin levels mean increased insulin resistance.
• Increased body fat means increased insulin resistance.
  • The  fat cells have absorbed excess energy which they now want to expel
  • Increased insulin (due to carbs) causes energy to leave the bloodstream and go into fat. The energy starved body now needs more food. This food (carbs) then elevates the insulin levels. This cycle would go on forever unless the body generated some insulin resistance. 
•  Our weight set point is the amount of fat and insulin resistance the body needs in order to supply energy to the body
  • In order to get energy out of their fat cells, the obese require engorged fat cells and significant insulin resistance to give energy to their body despite their very elevated insulin levels
• It follows that the obese are not “well-fed”, they are malnourished. The food they eat goes into fat and they have difficulty accessing it.
  • This explains the sluggishness found with the obese
  • And reproductive difficulty (for example, ovulation stopping) – they are starving and ovulation stops when animals are starving

If You Enjoyed This Summary, You Might Also Like

• Reflections from a 13 day water fast
• Hacks to take your fasting to the next level

Acknowledgements

In addition to Gary Taubes, I would like to thank Dr. Jason Fung and his wonderful book The Complete Guide to Fasting, Dr. Rhonda Patrick for her wonderful podcasts on fasting, Dr. Shawn Baker and Zack Bitter the carnivores of the Human Performance Outliers Podcast and the deep and insightful Amber O’Hearn.

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[i] Similar to Pavlov’s bell causing dogs to salivate. I wonder if there is a correlation of saliva production and insulin production. I definitely notice a correlation between cravings and saliva production. If I imagine or smell something delicious I salivate.

[ii] Dr. Fung’s book “The Complete Guide to Fasting brings many anecdotes of this phenomena.