Why am I suddenly gaining weight? The scientific answer

What causes weight gaining

Why am I suddenly gaining weight? Today we are going to talk about something that is generally quite interesting for society, which is how to lose weight. 

We've seen different diets and strategies that are often not and that they have little use.


Let's break it down in detail from psychoneuroimmunology that there is truth, that there is no truth, and because we gain weight or because we don't manage to lose weight.

In this article, we will see Why am I suddenly gaining weight? What causes us to lose, keep, or gain weight?

  • Keep our body Weight. We eat the same calories we spend.
  • Weight Gain. We take in more calories than we spend.
  • Lose weight. We take in fewer calories than we spend.
Table of Contents

Why am I suddenly gaining weight?

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Different control systems in the human body keep us from taking in more calories than we need and keeping from taking in less.

If we ate fewer calories than we needed for life, we would be at risk of death.  So physiology has already prepared us to be hungry to the point of covering our energy needs.

Stomach distension

He has also been concerned with finding a physiological strategy that tells us when we're full.  That first strategy has to do with stomach distension. 

The stomach's size is from an evolutionary point of view, physiology, and anatomy to ingest foods rich in fiber and water, such as fruits and vegetables.

Why an I suddenly gaining weight?

These foods rich in fiber and water have a lower caloric density than the refined products of Western society.

What happens when I eat foods such as fruits and vegetables that my body's anatomy and physiology need?  I eat these foods plus fish, meat, and then I feel satiated by a certain number of calories.

When I eat refined foods with a caloric density substantial, the size they have to occupy in our stomach to generate stomach distension is greater.

That's one of the mechanisms by which we eat more calories than we should. We choose foods with a much higher caloric density concerning their size, which generates stomach distension.

So the first indication is to choose unrefined foods such as fruits, vegetables, fish, and meat.

Food processing by the Gut Microbiome 

The second indication that we have to take into account is not only that we have a less distended stomach. But also the processing of food by the  Gut Microbiome.

Different studies have seen both mice and humans as an enrichment of 20% of the firmicute phylum (a type of bacteria a type of bacterial phylum present in our bacterial flora) results in absorption of 150 kilograms of calories with the same food intake.

That means that our Gut Microbiome will determine more or less ease of eating more or fewer calories.

We have to take into account mainly those who, for example, gain weight too quickly, are the Gut Microbiome.

Food choice

Another part that, although it seems evident and essential, is the choice of our food. 

  • If I choose the right foods, i.e., fruits, vegetables, meat, and fish, it is difficult to overdo in calorie intake.
  • If I select refined products, it is easy to overdo it in calorie intake, as we have seen before.

Food choice is not just a decision of the will. Now we are talking Fungal Microbiome. These can make us choose certain refined products such as:

  • Sugars.
  • Flours.
  • Also, certain dairy products that are high in calories.

An unbalanced ecosystem of microorganisms makes us that:

  • We ingest and absorb more calories from the same amount of food.
  • It also makes you choose the wrong foods, i.e., refined products.

Our subconscious

What causes weight gain? As we mentioned before, the choice is not only part of the will. 

There are also mechanisms of the subconscious that associate, as in Ivan Pavlov's "Conditioned Reflexes," certain moods with the choice of certain foods.

We can think about that quickly when we see those people who are trying to quit smoking. When they drink coffee or alcohol, the need to light a cigarette immediately appears.

The same thing can happen with children during childhood or growing up in certain situations.

For example, a child falls, hits himself, and then he has to stop. Usually, if we want him to stop crying, we give him candy. That way, I distract his attention.

That child will learn in his subconscious that in certain situations of suffering, it is good to choose refined products.

It would be more convenient when he suffers a physical injury let him cry calmly; in any case, a hug and tell him, cry, it is ok, nothing happens, the pain will go away.

Environment stimulation

Why am I suddenly gaining weight? We must bear in mind that our nervous system is ready to assimilate a certain number of stimuli.

There are several studies on hunger that say that when we see food, we immediately begin to secrete a series of hormones that will have to do with digestion and the endocrine system. 

In an environment like the one we live in, with so many visual and olfactory food stimuli, it is difficult for anyone to choose under real hunger.

A hunger where it wasn't over-stimulated to be able to choose when eating and when not to eat. I may not be hungry, I smell some pancakes, and I feel like eating those pancakes immediately.

That's not real hunger. It's a stimulus that awakens the neurophysiology appetite for something in particular. It's one of the mechanisms that will make us eat more calories than we need.

Something as simple as that but not because it's simple is less critical. 

Ease of getting caloric foods 

weight gaining

In that same line, how easy it is to get these foods, and on top of that, they are very caloric. 

Our biology understands getting food before making an effort. That is, I get food through:

  • Fishing.
  • Harvesting.
  • I have to search for food from the tree.
  • Hunting.

In our society, since the invention of refrigerators and supermarkets, we have a lot of refined food within our reach.

We get it so quickly that it's hard for us to say well today I'm hungry enough directly:

  • Get some food, and then I move on.
  • I'm going to get an apple from a tree and climb it.
  • I'm going to fish and look for a solution through movement to find food and spend calories.

Nowadays, we get up, go to the refrigerator, and have a fridge full of refined and processed products.

A lot of refined products that we have seen where we were going to buy, and our nervous system could not say no.

Our nervous system is prepared for when there is food to be eaten. If the environment is over-stimulating us with the presence of food, we will have no choice but to take it.

Addictive foods

Why am I suddenly gaining weight? The food industry knows how our reward and satisfaction circuits work through the palate.

Incredibly, addictive substances are allowed in products that we can find in all supermarkets.

There's a book I invite you to read entitled "Why humans like junk food?."

It explains the mechanisms that the food industry uses to generate: 

  • Addiction to products.
  • As a result, more sales of these.
  • More consumption and, therefore, more profit.

The food industry is looking for more sales, not more health. In that line, we have to make an exercise of responsibility.

We must understand that we can use certain products refined in particular situations or of the party. Those products used in a constant and repeated way in our day to day will harm us.

One of the mechanisms through which they will harm us is:

  • Because they are very dense in calories.
  • They will generate an imbalance in the formula of caloric intake and expenditure of calories.

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Sugared drinks 

Sometimes it's not even hunger; sometimes it's thirst. When we repeatedly ingest sweetened or sugary beverages, we confuse the Hypothalamus.

We give it a signal (due to the intake of so many calories) that we are eating, not drinking

The control of thirst and hunger at the cerebral nuclei level is in the Hypothalamus, specifically in the Arcuate Nucleus

The consumption of these drinks completely confuses itOur body loses the sensation of thirst, and what it does is eating permanently all day long. 

Leptin Resistance

To finish the last mechanism, I want to talk about is the resistance of leptin. Leptin is a hormone or a molecule that our bodies produce in our adipose tissue's fat cells. 

This hormone is responsible for giving the sensation of satiety at a hypothalamic level.

Excess leptin causes a loss of sensitivity at this middle level. That causes us to find people with visceral fat who need to eat more than they should because they have lost the biological signal of satiety.


Why am I suddenly gaining weight? Leptin resistance, added to all the above mechanisms, causes them to eat more calories than they touch. 

As a consequence, if we don't spend everything we eat, we will gain weight.