Why do we get fat?

Welcome to The Responsible Human, where we believe that your health is your first responsibility.

We will cover why being overweight/obese is a problem at all, how to calculate your BMI, what is the importance of Fat, what happens inside the body when we eat food, why does our body store fat in excess, and what scientific literature can we use to get rid of the excess weight. Before beginning, please note:

“This website does not provide medical advice It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment.”

Let’s begin.

Why is being overweight/obese a problem at all?

Being overweight or obese means having more body fat than considered healthy.
“Obese” means having a much higher percentage of body fat than “overweight”.

Body fat is important for purposes such as energy, heat insulation, and many other bodily functions. Having too much on the other hand, can cause serious health-related issues. High amount of body fat increases the risk for diseases such as diabetes, kidney disease, heart disease.

Another thing to note here is that the storage location of this excess fat can also increase the risk for health problems. For instance, the greater the amount of fat around the waist, the greater the risk.

Calculating your BMI (Body Mass Index) is one of the simple ways (next to looking in a mirror) to identify if you are overweight or obese.

To calculate your BMI, multiply your weight in pounds by 704.5 and divide the result by your height in inches, then divide the result by your height in inches.

A BMI between 25 and 29.9 is considered overweight.
A BMI of 30 or more is considered obese.

Note: BMI is used to estimate body fat, not measure it. For example, if you have a muscular physique, your BMI can still fall in the overweight range. A mirror would be useful in such situations though or even a body fat-measuring scale which you can easily find on Amazon. The link for an online calculator for BMI is given at the end of this article.

For children and teenagers:

BMI for children and teens is calculated differently than it is for adults.

For the calculation, the child or teenager’s height and weight are compared against growth charts that take age and sex into account. The result shows how a child or teenager’s BMI-for-age percentile compares with other boys and girls of the same age.

The 85th to less than 95th percentile is considered overweight.
The 95th percentile or greater is considered obese.

Importance of Fat

In a previous article “Why do we eat and how to do it right? – PART II” we learned that one of the main purpose of storing fat (in addition to the other ones you will in that article) is to serve as an energy reserve.

This stored fat is used as energy to survive in periods of no food availability.

A lean 75kg person has almost over 100,000 kcal stored in the form of fat. If our bodies had to store this energy in another form, for example, glycogen (stored form of carbohydrates), the weight would increase by 40kg to 60kg since glycogen is less energy-dense and is stored in combination with water.

However, the problem arises when our body starts storing too much fat.

How does the body store fat in excess?

Whenever we eat, a whole lot of metabolic processes start inside our bodies. Lets take a high level look on what happens when we eat.

When food enters our mouth, enzymes in the saliva break down starch (carbohydrates) to sugar, which travels to the stomach. In the stomach pepsin and HCL break down food to create what is called “chyme”. Chyme is then sent to the duodenum where bile is sent by the liver through the gall bladder. Bile dissolves fat in water for easy absorption. Also, enzymes secreted by the pancreas break down the food further to create a fluid form. The end result passes to the small intestine. In the small intestine sugar, fat and protein are separated.

Sugar goes directly to the blood and all the organs take up the sugar they need.
Some sugar is stored in the liver as glycogen, which is used for energy when required.
Whatever sugar is not used or stored is converted to fat and stored in fat cells.

Fat goes to the liver through blood. Some of it is burned by the liver, and some is sent to fat cells to be stored.

Protein is broken down into peptides which then are broken into amino acids. You can read more about the various functions for which these amino acids are used in the previous article “Why do we eat and how to do it right? – PART III“.

Any excess protein is either excreted in the form of urea or stored as fat.

From this process we can understand any excess calories not used by the body are stored as fat, to be later used as energy.

So is it all about Calories in vs Calories out?

The above explanation might give you an idea (which is already popular) that in order to lose weight,, the simple solution would be to take in less calories than we burn. Which also means, eating more calories than we burn should result in weight gain.

However, that also gives an idea that “a calorie is a calorie” no matter what the source. This is simply not true as evident by a multitude of research that different sources of calories produce different metabolic and hormonal responses in our body.

Also, this idea has almost been already bashed by the famous Keto Diet.

Furthermore, here is a person “Sam Feltham” who experimented on himself by eating more than he burned (he ate 5794 calories, cycled 40 minutes 3 times a week, performed 3 strength training sessions a week making his daily caloric expenditure 3058 calories, making his diet in a caloric surplus). He did not gain any weight at the end of 21 days. The majority of his diet was coconut oil, almonds, fish, spinach, broccoli, eggs.

Why? The research says that our bodies are smart, as we increase our energy intake, our bodies adjust by increasing its energy expenditure, which could be in the form of generating more heat or other metabolic activities.

The opposite of that is also true. When we are in a caloric reduction, our bodies compensate by decreasing metabolic function, decreasing body temperature, and making us hungry, because it does not want to DIE! And when this “so-called” diet of caloric reduction ends and we return to eat the normal amount of food we used to eat before, the body responds by not only gaining the amount of fat it had before but some more!

So, if the model of calories in vs calories out is not the way to go, what is?

Enters, the “Hormonal Hypothesis”

The hormonal hypothesis takes into account the various hormones produced in the body when we eat or do not eat and how they affect our hunger and fat storage.

Dr. Jason Fung is one of the proponents of this idea and has written numerous books such as “The Obesity Code, The Diabetes Code, and The Complete Guide to Fasting” covering it. Let’s explore what this hormonal hypothesis tells us and how Dr. Jason Fung looks at it.

In his series of “Aetiology of Obesity”, Dr. Jason Fung explains that one of the key hormone that drives obesity is Insulin.

Insulin was discovered in 1921 by Banting and Best at the University of Toronto. The discovery of insulin led to a cure for the disease called “Type 1 Diabetes”. In type 1 diabetes body attacks the cells (beta cells) that produce insulin in the pancreas, this results in extremely low levels of insulin which results in a tremendous amount of weight loss.

That tells us that absence if insulin results in weight loss. What about weight gain?

In a study where 2 groups with people having type 2 diabetes, one group was given more insulin than the other group. The initial weight at the beginning of the study was the same in both groups. The result? The group with higher doses of insulin gained more weight.

What does that tell us? Insulin causes weight gain, or obesity. Insulin tells the body to be in fat storage mode.

How does Insulin work?

When we eat certain foods, blood sugars rise and the pancreas releases insulin to control it. Insulin tells the body to move the glucose from the blood and store it for later use.

As we learned before, one of the places where this glucose is stored is in the liver, in the form of glycogen. However, the glycogen store is limited. Once it is full, if other cells are not accepting glucose (such as muscle cells if they have not been used much), the rest of the excess glucose is turned into fat.

Insulin also turns on fat production in the liver. This new fat can either be oxidized for energy, however, since insulin is already signaling that lots of energy is available, that does not occur. Next, the fat can be sent to other organs. Finally, the fat can be stored in the liver.

After the digestion of a meal is finished, the opposite effect starts to take place, the glycogen is converted back to glucose to be used by the brain, muscle, and other organs. This happens when we fast or at night if we are not constantly snacking. When glycogen stores get empty, fat is burned to release energy.

Does only food increase insulin?

You might know someone, who gains a little weight for a while, change their diet, and lose it easily. You might also know someone, who no matter what diet they follow, they are not just seeing results. The problem here is that, how long you have been overweight/obese matters a lot when it comes to losing weight.

Why so you ask? Let’s understand.

Insulin works by binding to the receptors on the cells and opens them so they can accept glucose from the blood.

Over time, cells develop resistance to the insulin, due to which the body has to produce more and more insulin to shove the glucose in the cells. This creates a vicious cycle, as resistant cells do not accept glucose, more insulin is produced, cells get fatter and fatter, increase resistance further, body produces more and more insulin to open them up.

Now, a person with insulin resistance starts a low-carb diet and several months pass by and he sees no weight loss because the higher levels of insulin are being produced due to already resistant cells, not the amount of carbohydrates ingested.

Why do cells become resistant?

This could be explained by the same reasons that result in antibiotic resistance (higher doses will result in bacteria resistance to the drug), caffeine resistance (the more you take, the more you will need down the road to feel the same effect), and also for cocaine resistance.

Preventing Insulin Resistance

Hormones and high levels of certain hormones are not necessarily bad for the body. The only thing is that there is a correct time for these hormones to be at a high level. For example, in the morning cortisol is high, which is a good thing, that is what wakes us up and starts the day. Constant high levels of cortisol throughout the day however are bad (which can happen due to stimulants such as coffee or stress).

It is the same story with insulin, infrequent high levels of insulin throughout the day are not an issue as long as it is balanced with low levels (for example, by not snacking between the meals or practicing intermittent fasting).

(And that particular mechanism is the reason I switch to decaf coffee every three weeks to avoid caffeine resistance, but that is an article for another time).

Coming back to the topic, Dr. Jason Fung also explains one interesting point, that insulin has different effects on different parts of the body. The major organs muscle, liver and brain have different sensitivity to insulin. Therefore, exercise increases insulin sensitivity in muscle cells, so they accept more glucose, however it does not affect the sensitivity/resistance in the brain or liver.

Liver insulin resistance, which is the result of eating too many carbohydrates, increases insulin levels in the body, however it does not affect the brain’s sensitivity to insulin. Which means, these high levels of insulin are still binding to the receptors in the brain which in turns tells the body to increase weight, as the brain manages hunger and calories burned.

So the solution seems simple, to let the body not adapt to high levels of insulin, by balancing it with periods of low levels.

How do you lower the levels of insulin? – Less frequent snacking and Intermittent Fasting (Not eating anything except Water, Black Coffee or Green Tea for at least 12 hours, and eating in a time-restricted window such as 8 AM to 8 PM).

I hope this has given you some idea about why do we get fat and what can we about it. Please note, there are more areas that are not covered here, such as are all carbohydrates bad? Do protein and fat raise insulin?, We will cover that in future articles. For now, I will leave out with short pointers which I hope help you.

Protein also increases insulin levels (such as whey, cheese, fish), however not as high as carbohydrates.
Dietary Fat results in the lowest increase in insulin levels.
Natural Whole Carbohydrates such as some fruits and vegetables are not dangerous as refined carbohydrates, since they contain vitamins, minerals, and fiber.
- Processing of food is what reaps it of nutrients. Be it, processed juice, processed flour (white flour), or even processed oil (Such as Vegetable Oils).
- Also, it is much difficult to overeat whole foods (think having to eat 5 apples vs having a glass of juice made with 5 apples. get it?)
ALSO, Not only Insulin, but Cortisol (knows as the stress hormone) also plays an important role in fat gain.

Do you have questions, feedback or a story to share? Make sure to leave them in comments! Cheers.

BMI Calculator: Adult BMI Calculator