For decades we have been told that to lose weight just eat fewer calories than you burn.
"Calories in, calories out."
Easy, isn't it?
But this equation, simple, reassuring and straightforward, is also deeply wrong, if we talk about humans and not of laboratory ovens.
What is really a calorie?
A calorie, by definition, is the amount of energy required to heat 1 gram of water of 1°C.
In the food context, we actually use the kilocalorie (kcal), that is, 1,000 calories: the amount of heat generated when you burn A food in a calorimeter.
But the human body is not an oven.
It does not "burn" food to generate heat.
It does not measure energy in kilocalories.
It does not convert 100 kcal of sugar and 100 kcal of fat in the same way.
E never behaves like a linear machine.
The body does not use heat: it uses ATP
At the cellular level, the true biological energy unit is not the calorie, but theATP (adenosine triphosphate).
It is ATP that powers your muscles, your brain, your heartbeat.
And the production of ATP depends on many factors, not just by how many "calories" you eat.
Calories are only potential energy
Take a steak or a glass of wine: On paper they could have the same caloric content.
But in the body:
- Metabolic pathways change
- Activated hormones change
- They change the tissues that will use or store that energy
Wine will raise insulin and overload the liver.
Steak will stimulate glucagon, protein synthesis and thermogenesis.
Same number of calories? Yes.
Same biological effect? Absolutely not.
The myth of energy output
"You burn more than you eat."
But how much you burn Depends on:
- The quality and composition of the food
- Your hormone profile (cortisol, insulin, androgens, thyroid...)
- Your sleep, your sunlight, your body temperature.
- Your mitochondrial efficiency
- Your digestive and absorptive capacity
- Your level of stress, inflammation, disease
- The type of movement you do (walking ≠ sprinting ≠ weights)
The body is not passive. È adaptive.
When you eat more, the body may decide to spend more (more heat, more spontaneous movement, more anabolic hormones).
When you eat less, the body can slow everything down (less thyroid, less heat, less vital drive).
This is called metabolic adaptation.
🧬 Hormones decide where energy goes
Do you want an example?
- In a state androgenic (high testosterone): calories go toward muscles and bones.
- In a state cortisol (chronic stress): the same calories can go toward visceral fat, inflammation and muscle catabolism.
📌 Same caloric "input."
📌 Opposite metabolic results.
Interesting data:
Two people eating the same amount of calories, with the same macros, can:
- gain or lose weight differently
- accumulate fat in different areas
- Change their lean mass, insulin sensitivity, mood, thermogenesis
The body doesn't add up the calories like on a calculator.
Challenges interprets them, adapts them, directs them.
Two people, one pizza - same food, different effects
Imagine two people:
- same height
- same weight
- same number of calories consumed in the day
- same pizza on the plate
But with one important difference: the physiological context:
🔹 Person A has a healthy metabolism:
- High testosterone
- Thyroid hormones in balance
- Low cortisol
- Active muscle mass
- Excellent insulin sensitivity
- Deep sleep
- Mitochondria functioning as nuclear power plants
🔹 Person B, on the other hand, is in an altered metabolic state:
- Low Testosterone
- Slowed thyroid
- Chronically high cortisol
- Systemic inflammation
- Unstable blood glucose
- Little sleep, little sunlight
- Lazy, stressed mitochondria
Person A probably:
✅ will use that pizza to replenish muscle glycogen
✅ will stimulate an anabolic spike
✅ will burn the meal quickly due to active lean mass
✅ will be back in balance in a few hours
Person B, on the other hand, could:
- cause a more pronounced glycemic surge
- Stimulate more insulin to compensate
- promote the accumulation of visceral fat
- Increase drowsiness, subsequent hunger or inflammation
The point is not to demonize food
The pizza itself, Is not "good" or "bad".
But the way in which it is assimilated, managed and addressed depends on who eats it and in what metabolic state is found.
The body does not receive food as an abstract datum. It interprets it.
And it does this through the filter of your hormonal, digestive, inflammatory, mitochondrial and nervous state.
The truth?
Calories in, calories out is like saying that the efficiency of a car depends only on how much gasoline goes in and how much comes out - ignoring the engine, the type of fuel, the oil, road conditions, e the driver.
It is a simplification useful only for nutrition labels and databases.
Not to really understand how the human body works.
What really matters?
If you want to manage energy, metabolism and body composition, look beyond the numbers:
- La quality food
- The type of nutrients (protein ≠ carbohydrates ≠ fat)
- The timing (eating at midnight ≠ eating breakfast)
- Your hormones, your sleep, your circadian rhythm
- Your mitochondrial resilience
Calories are only one of many variables. And not the most important one.
Conclusion: yes, the deficit works - but at what price?
For the avoidance of doubt, it is only fair to state this clearly:
If a person introduces less energy Than it consumes,
the body will be forced to draw on its reserves (body fat, but also muscle).
📉 This means that. Slimming down is possible even in a dysfunctional metabolic state.
But at what cost?
🔴 Yes, the unoptimized person will be able to lose weight....
But the price to pay will be high. Much higher than it seems.
In the process:
- will be more and more tired, plus hungry, plus irritable
- sleep will get worse, the thermogenesis will drop, will begin to feel constant cold
- the concentration Will decrease, the mood will drop
- will disappear the motivation, the desire to move, of socialize, of live energetically
And the longer it goes on, the more the body will slow everything down: metabolism, hormones, energy, desire.
It will be a forced march against nature.
He will lose weight, yes, But that weight won't just be fat: it will also be muscle mass And in some cases, more muscle than fat, especially if does not train And does not consume enough protein.
Then what?
Once he reaches "target weight"- (assuming he hasn't given up before) - will suffice resume eating normally To see:
- the weight rise quickly
- the body accumulate fatter than before
- hunger become more intense and uncontrollable
- the signs of satiety completely out of whack
The brain, deprived for a long time, reacts with compulsiveness and it's like could no longer stop. And very often it fails.
🟢 The "optimized" person, on the other hand...
Even with a moderate energy deficit, will be able to:
- ✅ losing mainly fat, saving the muscles
- ✅ maintain energy, mental clarity, vitality
- ✅ sleep better, regulate appetite, retain motivation
- ✅ react well to a return to a normocaloric diet, recharging the tissues instead of fattening
It is a qualitative difference, not only quantitative.
In summary?
Yes, it is possible to lose weight by "flagellating" yourself through restriction, starvation and discipline.
But it is an uphill path, which the body lives as a stress, not as an evolution.
A person can also lose 30 pounds by willpower alone, but if he loses muscles, energy and hormonal health, then he just won a battle against the scale, non-organic.
The real goal is not lose weight at all costs, but to create a body that function so well that you can lose weight easily, almost without thinking about it, and then no longer resume What he let go.
The real goal is to be well And that is what I wish for you as well.
Love,
Oliver
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