What happens if we stop eating?
We hear more and more about fasting, therapeutic fasting, etc. But what really happens in our bodies when we choose to stop eating for several days?
less than 24 hours
The body uses glucose naturally found in the blood or in the liver in the form of a reserve (glycogen), to provide the energy that all cells need. Glucose, in a way, is the fuel for our bodies.
By 24 hours, the body does not yet alarm and continues to function more or less as usual.
Between 1 and 5 days
After 24 hours of not eating, glucose and glycogen stores begin to deplete. So the body adjusts its energy management and begins using muscle (proteins) and adipose tissue (fatty fat reserves) to ensure adequate intake.
However, the loss of muscle mass is very limited and gradual during a period without food. The loss of strength and loss of muscle mass is not surprising when you fast for just a few days. Our body adapts and does not overly rely on its muscle reserves. Prefer more fat reserves.
After 5 days
From 5 days, and sometimes a little earlier (day 3), our body regulates itself differently to avoid relying on protein (muscle) reserves. He understands that he really can no longer rely on an external energy source and significantly adjusts his metabolism.
The liver and kidneys then produce ketone bodies that the brain uses to replace glucose. These ketone bodies are made from fat stores. This is a path that is sometimes difficult to pass.
The mass losses observed during fasting are mainly explained by the loss of water (hydration), the loss of fat mass (adipose tissue) and finally by muscle wasting. So the latter is very progressive.
An average adult person measures 1 meter 70 per 70 kilograms theoretical fat reserve that allows them to go for 40 days without eating.
In theory, an adult of the same size but weighing 90 kg (including 25 kg of fat) could last 100 days!