Satiety per Calorie: Eating, solved.

Table of Contents

Satiety Per Calorie

Table of Contents

About The Author

Introduction

1/4: How Eating Works

Understanding Eating

Plants vs. Animals

Photosynthesis

Nitrogen and Minerals

Nutrient Requirements

Understanding Digestion

Protein Digestion

Carbohydrate Digestion

Fat Digestion

Understanding Storage

Carbohydrate Storage

Fat Storage

Metabolic Fuels

Insulin Versus Glucagon

Understanding Metabolism

Metabolic Rate

Components of Metabolism

Mitochondria and Oxidation

Dual-fuel Hybrid Engine

Calories Versus Carbons

Glucose Versus Fat

Carbohydrates and Ketosis

How Eating Works: Summary

2/4: How Eating Breaks

The Satiety Crisis

Overweight and Obesity

Epidemic Proportions

Obesity and Chronic Disease

Overfatness

Running Out of Storage

Personal Fat Threshold

Insulin Resistance

Energy Toxicity

Type 2 Diabetes

Why We Overeat

Carrot And Stick

Obesity and Evolution

Eating Economics

Needing To Overeat

Protein Leverage

Protein Dilution

Micronutrient Dilution

Caloric Density

Wanting To Overeat

Evolutionary Perspective

Food Reward

Energy Density

Human Junk Food

Carbs + Fat

Refinement of Carbs and Fats

The 'Bliss Point'

Thermic Effect

How Eating Breaks: Summary

3/4: How To Fix Eating

The Solutions So Far

Satiety

Defining Satiety

Satiety Signaling

Incretins

Incretin Pharmacology

Satiety Timescale

The Goldilocks Principle

The Law of Diminishing Returns

Hormesis

Appetites

Protein

Fat

Carbs

Minerals

Hedonic Appetite

Target Levers

Increase Protein

Increase Fiber

Increase Water

Increase Micronutrients

Increase Weight And Volume

Increase Oral Processing Time

Increase Surface Hardness

Reduce Levers

Decrease Non-fiber Carbs

Decrease Nonessential Fats

Decrease Alcohol

Decrease Energy Density

Decrease Processing

Slow Eating Speed

Slow Digestion Speed

Food Variety (Sensory Specific Satiety)

Serving Size

Hunger and Fullness

Hunger And Fullness Scale

Mindfulness

Intermittent Fasting

Hedonic Reset

Hydration

Thirst Versus Hunger

Exercise

Sleep

Stress Management

How To Fix Eating: Summary

4/4: Putting It All Together

Why ‘Eating Less’ Isn’t Enough

Satiety Scoring

The Satiety Score

U-Shaped Curve

Dichotomous Thinking

Possible versus Optimal

Validity versus Necessity

Body Recomposition

'Eat Less'

'Move More'

Energy Flux

Caloric Deficit

Exercise

Resistance Training

Resistance Training Movement Patterns

Upper Body: Push

Upper Body: Pull

Lower Body: Push

Lower Body: Pull

Full Body Workout

Minimalist Routine

Using Machines

Muscle Hypertrophy

Genetics and Consistency

Cardio

General Movement

Physical Activity Level

Exercise Progression

Perfection Does Not Exist

Food Choice

Positive Reframing

Protein / Fiber / Water First

Choosing Protein Sources

Animal vs. Plant Protein

Protein Staples

Non-Protein Energy Density

Non-Protein Staples

Reduce Refinement

Avoid The Trifecta

Progression

Calories

Reading Nutrition Labels

Satiety Scoring: A Useful Construct for Better Eating

Increasing Your Satiety Score

Tracking Macros

Ideal Body Weight

Protein Distribution

Carbohydrate Distribution

Fat Distribution

Protein Grams

Carbohydrate Grams

Fat Grams

The Power of 3

Cooking and Eating

’S' for Satiety

Beverages

Meal Options

Breakfast

Lunch

Dinner

Snacks

Dessert

Daily Goals: Protein, Weight, and Volume

Recipes

Sustainability

Habits

External Setup

Fake It Till You Make It

Health, Wealth, and Relationships

Conclusion

References

GENERAL

PROTEIN

ENERGY DENSITY

FIBER

HEDONICS

Author’s Note

About The Author



In addition to being a husband and a father, Dr. Ted Naiman is a board-certified Family Medicine physician in the department of Primary Care at a leading major medical center in Seattle. He is a clinical faculty member of the University of Washington School of Medicine in the department of Family Medicine. His research and medical practice are focused on the practical implementation of diet and exercise for health optimization. He has an undergraduate degree in mechanical engineering. He can be found on all social media platforms under the handle @tednaiman.

Introduction

It took me a while, but somewhere during my quarter-century in primary care medicine it slowly dawned on me: everyone is overfat. Well, not literally everyone—but nearly. Almost everyone has become overfat (meaning they have more fat stored than is optimal for health). It's pretty obvious for the majority. I only have to glance at them from across the room or maybe look at the BMI, or body mass index, printed at the top of their chart in a bold red font to see that they are clearly overweight or obese—categories that now describe 75% of America. But even among my patients who look visibly normal weight or even lean, some disturbing things showed up. Waist circumference, not your pants size but instead your abdominal circumference measured at the belly button, was often more than half of height—an indicator of excessive visceral fat even in visibly lean persons. Fasting triglycerides over 100 mg/dL (1.13 mmol/L)—an early warning sign that your fat cells are too full so this triglyceride fat has no place to go. And then there are all the diseases linked to 'insulin resistance', a fancy medical term for overfatness. Sure, all the big scary diseases are included, like cardiovascular diseases, autoimmune diseases, and neurodegenerative diseases like Alzheimer's dementia. But overfatness, as indicated by insulin resistance, also contributes to a host of common medical conditions like acne, acid reflux, and arthritis, just to name a few. All seem to be driven by the metabolic disturbances of overfatness that now afflict over 90% of Americans, and most of these are improved by the metabolic health upgrades that result from fat loss. In the medical literature, anything that decreases overfatness seems to improve virtually any health parameter you could measure, as well as improving symptom scores for the vast majority of chronic diseases.

So how did we get here? Three-fourths of the world is now overfat, and an estimated 90% or more of Americans. And the crazy part is, absolutely nobody wants to be overfat. Most of my patients who suffer from obesity tell me they would pay almost anything to be leaner, and I believe them. If there is anything I have learned from decades of medicine, it is that without your health, nothing else matters. So why wouldn't you trade almost anything else for health improvements? The ultimate goal in life for most humans is happiness. Think about anything in life that you want, and if you really go down the rabbit hole of, why do you want that thing, it is ultimately, to be happy. But it is really hard to be happy about anything without your physical health. If you don't look good, feel good, or perform well physically, happiness is going to be, to some extent, out of reach. So we have this completely unprecedented situation, where the majority of humans on earth would do anything to be happy, and would do anything to have physical health so that they can look, feel, and perform optimally—and yet this is not happening for so many people due to our epidemic of overfatness.

Something is broken. Is it our genetics? Well, 70% of obesity does seem to be genetically determined, something we have seen demonstrated over and over in identical twins studies. But human genetics change very slowly, over tens of thousands of years, so this really doesn't explain how obesity went from 1% two hundred years ago to nearly half of Americans and a large percentage of the world as well. So something has changed in our environment. We know that our food has changed, but what exactly about it has changed, and how has this contributed to the global obesity epidemic? And the logical all-important follow up question is, exactly what can we do about it?

You may not believe it yet, but the main difference between someone who is gaining weight versus someone who is losing weight comes down to one concept: satiety per calorie. Satiety is the opposite of hunger. Satiety is the satisfied feeling that you have when you have eaten enough food, and no longer have any hunger or desire to eat further. I get it, you don't believe me. But let's do a thought experiment. We are going to clone you right now, and your clone will go on eating the way you eat currently. But we are going to give you a special magical food that contains a ridiculous amount of satiety, even at very small quantities. For example, we are going to give you one tiny super satiety cracker that only contains 100 calories, but provides an entire day’s worth of satiety, meaning that after eating the cracker you are extremely non-hungry and really not motivated by hunger to eat any more food the rest of the day. So you eat this cracker, while your clone eats all of the things that you normally eat. What is going to happen to your caloric intake today? How about tomorrow? And what do you think will happen to your weight, compared to your clone? As you can see, satiety—and specifically satiety PER CALORIE, is extraordinarily powerful.

In this book, we are going to explore all of this in depth. We are going to learn about eating, satiety, and the changes to our food supply that worsened satiety per calorie by reducing the things that improve satiety while simultaneously increasing empty calories in virtually all of our modern foods. And finally, we are going to give you the very practical, actionable steps to take to slowly reverse this global trend and take back control over your body composition, metabolic health, and ultimately, happiness. By the end of this book, you’ll be able to explain nearly everything about diet and health in a framework that makes perfect sense. And you will walk away with lifelong knowledge of how diet really works, and how diet affects health. And you'll probably also say, Why didn't I think of that?

And away we go!

1/4:

How Eating Works



Plants are at the base of the food chain, creating all food for all animals.

Understanding Eating

When humans lack knowledge about physical phenomena, we make up some pretty crazy stuff. You don’t have to go back very far in history to see some extreme examples. The Earth as the center of the Universe seemed like a pretty good idea a few thousand years ago. A few hundred years ago, 'Spontaneous Generation' seemed like a great explanation for the appearance of new life. And it was only about two hundred years ago that bloodletting was no longer seen as a standard legitimate medical treatment for just about any ailment. Clearly, the more we know about how things work, the fewer strange and mystical religious beliefs we have to make up to explain them.

Eating is certainly no different. Until very recently, humans were in the dark ages when it comes to food and nutrition. Luckily this wasn’t a big deal in the past, as historically, anything edible in your food environment was probably good enough for survival. And in fact if we know anything about humans and food, it is that we are extremely adaptable survival machines. Humans can live in almost any environment on earth, eating almost anything edible. In some ways, this extreme adaptability has contributed to our eating confusion. Since it is POSSIBLE to live on almost anything, how do we know what is OPTIMAL? Can you live on only plants? Absolutely, and we have the vegan YouTube fruititarians to prove it. How about all animals? Yup, we have some carnivores to thank for this knowledge. High carb versus zero carb? Sure, take your pick. Mostly fat versus virtually none? Flip a coin! Examples abound.

These huge ranges of adaptability drive a lot of us into one of two directions. On one hand you have those who realize that you can survive by more or less eating absolutely anything you want, and from that point on their primary consideration is eating what tastes good. I think we can all see how this is turning out on a global scale (hint: not good). And on the other hand you have those who are desperate to make sense of it all. Perhaps the secret is eating only plants. Yes, that must be it. After all, Adam and Eve only ate plants, right? And since humans don’t ship with an Owner’s Manual containing some basic care and feeding instructions, we will have to turn to the book of Genesis, I guess? What if animal foods are actually dangerously bad? Maybe they rot in your colon for years and cause a bunch of chronic diseases! Okay, I’m definitely vegan now. But on the other hand, perhaps some plant foods are toxic—maybe gluten is silently poisoning everyone, and a strict Paleo diet is the solution! You can see how easy it is to jump straight on the flat earth bandwagon when you don’t really have a firm grasp on the real relationships between diet and health.

We will never get anywhere when it comes to diet unless we fully understand what eating is, and exactly how it works. And in order to do that, we have to start with some basics. Some of you know all of this already, and I give you permission to roll your eyes and sigh. But most of us really need this background so we can truly grasp the upcoming chapters. I will try to keep this as streamlined as possible, and I promise that this is useful information for absolutely everyone.



We’ll get to practical specifics later—but we’re starting out with the basics.

Plants vs. Animals

We humans like to think of ourselves as the dominant species on Earth. I mean come on, we have opposable thumbs, huge brains, and Netflix. But the reality is that animals in general are a huge minority when it comes to life on earth. If you look at sheer biomass, plants are crushing it. Plants are the base of all food on earth.



Plants are the largest biomass on earth, by a wide margin.

Plants are 'autotrophs', which means that they make all of their own food. Animals, in contrast, are 'heterotrophs', which means that they only stay alive by constantly eating either plants, or an animal that has eaten plants. We humans are only alive because we constantly eat other living organisms. This is how the entire system works. We are 'consumers', and we owe our entire existence to plants, which create not only all of our food, but also all of the oxygen in our atmosphere.



Autotrophs make their own food, and then heterotrophs eat them. Unfair, right?

In order to create all of their own food, and—unfortunately for them—all of our food, plants are doing two very specific things. First of all, they are performing photosynthesis, the process of converting solar energy into chemical energy. Second, they are absorbing minerals from the soil, most notably nitrogen, the primary ingredient of the amino acids that make up all of our proteins. We will explore these in the upcoming sections!

Photosynthesis

Plants perform photosynthesis. This process is powered by sunlight energy, and is the conversion of carbon dioxide in the atmosphere and water in the soil into chains of carbons which we classify as 'carbohydrates' or 'hydrocarbons'—better known to us as carbs and fats. Plants use these carb and fat carbon chains structurally, to build themselves, and also to store energy for future use. We animals then consume these carbon chains, break them down into individual sugar and fat molecules, and then store them to use for energy. Plants tend to store most of their carbon energy as carbohydrates in the form of sugars, while we animals tend to store most of our energy in the form of fat. We will go into a lot more detail on exactly how we store energy as fat and carbohydrate in upcoming chapters, but right now we are just establishing some foundational concepts.



Photosynthesis captures solar energy and transforms it into chemical energy, powering all life on Earth.

Animals require energy continuously, but we only ingest energy periodically. We are essentially battery powered. We continuously burn carbon chains in our mitochondria just to stay alive, and those carbon chains are steadily released from our fat cells into our bloodstream. Our stored fat is just like a chemical battery, and when we eat more carbons we are recharging this chemical energy. But the carbons that we store as fat originally came from plants, and the energy stored in the high-energy bonds between the carbons in these chains came straight from the sun. So in a way, we are all powered by solar energy, and that energy is captured as chemical energy by plants.



Plants turn solar energy and carbon dioxide into carbs and fats for animal life, and thus all of our carbon-based energy comes from photosynthesis.



This super nerdy glimpse of photosynthesis is only for the one person out there reading this book who actually likes chemistry.

Nitrogen and Minerals

In addition to photosynthesis—the capturing of solar energy as chemical energy in the form of high-energy carbon bonds—plants are also absorbing the minerals required for life from soil. There are four basic elements of organic life that make up 96% of your body: oxygen, carbon, hydrogen, and nitrogen. Oxygen, carbon, and hydrogen come from air and water. But nitrogen is absorbed from the soil, in mineral form. In addition to nitrogen, plants absorb another two dozen or so minerals that are required for both plant and animal life.

Most of these minerals are considered 'trace' essential minerals, with only tiny quantities necessary. But several of these are classified as 'macro-minerals', with requirements as high as several thousand milligrams per day: potassium, sodium and chlorine (together as sodium chloride in table salt), and calcium are among the most notable. Drinking water is also supposed to contain some minerals that contribute to our daily intake (mostly calcium, sodium, and magnesium), but this is highly variable and, even if your water happens to have some of these minerals, the vast majority of our essential minerals originate from soil and are then incorporated into plants.



Certain minerals, like potassium, need to be consumed in such large quantities daily that they are referred to as 'macrominerals'. Most of us get adequate sodium chloride (regular salt) in our diets, but note the special importance here of potassium and calcium, which will be discussed later!

So the big picture is that plants are providing every bit of the energy that keeps we animals alive, by storing solar energy in carbon chains (carbs and fats). And they also provide all of the protein and most of the minerals that make up our physical bodies, by absorbing nitrogen and other minerals out of the soil.



All of the elements required in our diets, as shown from the periodic table of the elements.



Plants get carbon from carbon dioxide in the air, but they absorb nitrogen for protein, as well as other mineral micronutrients, from the soil.



Plants produce all three of our dietary macronutrients. Carbs and fats are carbon chains with high-energy bonds that provide all of our energy. Protein, made from soil minerals, forms the basis for all of our structures and also all of the functions of our bodies.

Nutrient Requirements

Like all animals, humans have five basic nutrient requirements. We’ll review them here:



All animals require regular ingestion of these five things.

Water. Water, of course, is a requirement for every living thing on earth, and from this point on we will take it for granted, focusing on the food we eat instead.

Energy. Next on the list, in order of quantity required per day on average, are the three MACROnutrients, named 'macro' because we need fairly large quantities of them daily on average. But very specifically, the first category here is a macronutrient 'energy source'. Note that this is not carbs or fats exclusively, but either one of the other. All animals can burn some combination of the two, and humans are particularly adapted to a very wide range on the carb-fat spectrum, with the ability to survive on either very low carb high fat diets, or very low fat high carb diets. So we really have to lump carbs and fats together as just interchangeable carbon chain energy sources.

Amino acids. The next item on the list of nutrient requirements is protein. There are 20 amino acids that are common to all life forms, and while there are about half a dozen that we can synthesize from other dietary amino acids, ALL of the nitrogen for these proteins comes from our dietary protein. Humans need about 50 grams of protein daily just to stay alive and keep functioning somewhat normally (although likely not optimally on this sort of minimal protein intake). Most of us have enough stored energy in the form of fat to live for a month without eating any energy calories, but we have no ability to store protein. It is because we have no ability to store protein that our need for this dietary protein is more pressing than our need for energy on a day to day basis.

Fatty acids. Technically, the requirement for carbohydrate in the human diet is exactly zero. But there are just two specific fats that are essential to humans from the diet. We only need a few grams of these per day, but they are definitely a necessity.

Micronutrients. Finally we have vitamins and minerals. There are 13 essential vitamins and about twice as many minerals that we need in small quantities in our diet—thus the term 'MICROnutrients'.



Humans require 13 vitamins. Twelve are pictured here (B12 was omitted as it is a weird complicated molecule centered around an atom of cobalt). The water-soluble vitamins contain nitrogen and are thus similar to amino acids, which is where the '-amins' part of the name comes from (with 'vita-' having the same Latin root as the word vital).

Plants create all of these non-water macronutrients (carbs, fat, and protein) and micronutrients (vitamins and minerals) and then inadvertently package them and pass them up to the animals that eat them, as well as the other animals that might eat THOSE animals. This is the food chain as we know it, with plants at the bottom, then herbivores, then carnivores, and then apex predators. Humans, with our extremely flexible and adaptable approach to eating, are of course omnivores. Just as we can manage with extremes of carbohydrates or fats as a carbon energy source, we can also happily exist on nearly any combination of plants and/or animals. This flexibility has allowed humans to migrate and flourish in all corners of the earth, from the equator to the arctic.



Plants create all macronutrients and bioaccumulate minerals. Plants are then ingested by we animals—which is how we obtain all of the protein and minerals required to build our bodies, as well as all of the energy which allows us to function.

Hopefully you are now getting the big picture when it comes to the nutrients we need in our diets, where they come from, and how they get there. And stay tuned—later in this book we will talk more about the implications of the presence or absence of these dietary requirements in our food environment, and how these different components contribute to downstream outcomes such as satiety per calorie, and ultimately body composition and health.

Understanding Digestion



Digestion is the process of breaking down food into substances that can be used by the body.

Digestion is an incredibly complicated phenomenon, and you could fill many dozens of books this size with all of the minutiae and details and biochemistry. But to accomplish the goals in this book you really only need to know a few basic things here. You have already learned that there are really only three main dietary macronutrients—protein, carbohydrate, and fat. Now we need to break these three down into more digestible pieces—pun intended.

Protein Digestion



Protein is broken down into larger peptide subunits, then into individual amino acids.

The word 'protein' comes from the Greek word 'proteios', meaning 'primary' or 'holding the first place'. Proteins are insanely complicated, and there are approximately 20,000 unique protein encoding genes responsible for the more than 100,000 unique proteins that comprise the structure and function of your body. But despite the complexity of protein in general, the building blocks of proteins are much simpler. As mentioned earlier, all protein are comprised of individual subunits known as amino acids. There are several hundred amino acids found in nature, but believe it or not, it only takes around 20 basic amino acids to construct all of the proteins found in both humans and also most other forms of life on earth.



All life on earth is based on only twenty amino acids, and here they are. Crazy, right?

Digestion of protein, therefore, is actually fairly simple. Proteins are broken down, by digestive enzymes, into smaller chains called peptides, and then into individual amino acids prior to entering the bloodstream. After consumption, the level of amino acids in the bloodstream slowly rises and then gradually falls again over a period of several hours, the magnitude and duration of which depends on the amount of protein eaten (as well as some other dietary factors).

Carbohydrate Digestion

Glucose is a simple sugar molecule that is used for energy by every living thing on earth. It is the prototypical subunit of most carbohydrates. Carbohydrates are usually categorized as either 'simple' or 'complex', based on how many sugar molecules they contain. Single or double sugars (monosaccharides and disaccharides) are classified as simple carbohydrates, while longer chains of glucose are referred to as complex carbohydrates.



Carbs are either SIMPLE SUGARS (1 or 2 units), or COMPLEX (more than 2).

These larger glucose chains (known as polysaccharides) are either starches, which are readily broken down into individual glucose molecules prior to absorption, or fiber. Fiber is resistant to digestion. Some fiber, like the insoluble cellulose that plants use to form structural rigidity, resists digestion so much that it passes through the gastrointestinal tract with minimal changes. Other types of fiber are variably changed during digestion, and the less tough soluble types of fiber are often fermented to some degree by bacteria in the colon into short chain fats that can be used by these bacteria—as well as some of your cells lining your intestinal tract. We will talk more about fiber versus non-fiber carbohydrates later, as this will be important! Note that humans, like all mammals, lack the enzyme required to break down cellulose, which is why this fiber passes through our digestive tract intact. Herbivores, such as cows, that live off of grasses and other high cellulose plant foods, employ billions of bacteria which DO produce the cellulase enzyme necessary to break apart otherwise undigestible plant fiber, allowing the bacteria to ferment cellulose into fatty acids.

Fat Digestion

Dietary fat is consumed as 'triglycerides', which is the way that most lipids are packaged and stored in nature. A triglyceride consists of three fatty acid chains (just chains of high-energy carbon bonds, as discussed previously), all connected to a glycerol backbone (glycerol is a three carbon chain that is basically half of a glucose molecule). During digestion, fat is broken down into individual fatty acids and then absorbed, only to be repackaged again as triglycerides prior to heading for your fat cells, with possible delivery to any other hungry tissues such as muscle on its way. Because fat is not water soluble and your blood is mostly water, these fats have to be packaged in little water-soluble spheres that ferry the fat around like boats, known as 'lipoproteins'.

Fatty acid carbon chains have variable lengths, usually from 4-24 carbons each. They are called 'saturated' when they have no double bonds between carbons, and these fats are solid at room temperature. Unsaturated fats have one or more double bonds between carbons, and these fats tend to be liquid at room temperature. All of these fats are found in both plants and animals, but the saturated ones are more common in animals and the unsaturated ones are more common in plants. This is why animal fats such as butter and lard tend to be solid at room temperature, while plant fats such as olive oil and corn oil tend to be liquid.



Most fat is both ingested and also stored in triglyceride form.



Fats are classified as saturated (no double bonds) versus unsaturated (one or more double bonds). Unsaturated fats are further subdivided as monounsaturated (one double bond) or polyunsaturated (multiple double bonds).

Understanding Storage

Animals are essentially battery powered, with a chemical battery that stores carbon-based energy. We need a continuous supply of energy, just to be alive. Our basal metabolic rate, the amount of calories it takes just to breathe and circulate blood and perform other vital functions, is on average about 1,500 calories per day. We need a continuous and uninterrupted supply of energy, and therefore we have to carry some energy around with us at all times. Animals carry the vast majority of their energy around as fat, and we humans usually have enough fat in our bodies to last for weeks or even months without food, just in case we can’t find anything to eat. We are designed to burn calories continuously, trickling in from our fat stores, and then eat periodically in order to replenish this stored energy. Carbohydrate and fat are interchangeable as an energy source, but we store carbohydrate and fat separately—a requirement because carbohydrates are water soluble, unlike fat. Protein is technically not stored but is present in skeletal muscle, so if you are starving and unable to eat protein you are forced to break down some muscle tissue for amino acids, which is sadly the equivalent of breaking up the furniture in your house for kindling to stay warm in the winter if you don’t have any firewood.



Carbohydrates and fat are stored in separate compartments in the body. If you are eating more carbohydrate, you have to burn more carbohydrate, as carbohydrate storage as glycogen is much smaller than space for fat storage in adipocytes. And if you are eating WAY more carbohydrate your body will turn that into fat for storage as well, once glycogen stores are full.

Carbohydrate Storage

Carbon-based energy can be stored in multiple forms, but the two predominant forms in living creatures are carbohydrates and fats. Plants tend to store most of their energy as carbohydrate, typically as the long chains of glucose molecules known as starch that we discussed in the last chapter. We animals, however, vastly prefer to store most of our energy as fat. Why the difference? It really comes down to size and weight. Because plants are immobile, size and weight are really not factors when it comes to energy storage considerations. In fact, for an immobile plant, it might be beneficial to be as large and heavy as possible. But because animals are highly mobile, we have to carry all of our energy around with us. So naturally we are going to pick the smallest and lightest form of energy we possibly can.



This small vial of olive oil and this large bowl of potatoes each contains equal calories.

In animals, carbohydrate is stored as chains of glucose known as glycogen. Glycogen is very similar to starch, which is the plant version of stored chains of glucose. Because carbohydrates are water-soluble, they have to be stored with a lot of water. For every gram of glycogen we store, around three grams of water are stored along with this glycogen. This water requirement makes stored glycogen about six times heavier than stored fat, and about six times physically larger as well! We animals store this glycogen in our liver and also our skeletal muscles. The amount of glycogen we can store is fairly limited, with around 100 grams of glycogen storage in the average human liver and around 300 grams of glycogen storage in skeletal muscle of the average human. Only about 1% of our stored energy is in the form of this glycogen, due to its prohibitive size and weight requirements. Most people only have enough stored carbohydrate to provide only a single day’s worth of calories, while the average person can live for about a month on the calories in stored fat.



Stored fat is six times smaller and lighter, for the same amount of calories.

The carbs we store as muscle glycogen remains locked in our muscles, for emergency use by those muscles, and cannot be shared with the rest of the body.