Why the brain prevents weight loss: scientists explain how biology protects us from losing weight

But modern research shows that it's more complicated than that. Biology and the human brain are designed to protect the body from weight loss - even if it is necessary for health.

In an article for The Conversation, scientists Valdemar Johansen and Kristoffer Clemmensen explain: our brains still operate according to the laws of ancient times, when fat was a matter of survival. For our ancestors, extra kilograms meant energy, and not enough meant the threat of starvation. Therefore, the body developed a complex system of defence of energy reserves.

Today, when food is available everywhere and physical activity is minimal, these ancient mechanisms turn against us. When a person loses weight, the brain perceives it as stress: hunger hormone levels rise, food cravings and fatigue increase, and metabolism slows down.

According to the researchers, the brain is able to "memorise" the previous weight and seeks to return it, considering it to be the norm. For ancient people it was an advantage - it allowed them to recover strength after hungry times. But such "memory of weight" hinders modern people: after diets, the body tries to return the lost kilograms, even if the extra weight is harmful.

Scientists note that this is not a manifestation of weak will, but the result of biological mechanisms that are evolutionarily programmed to protect the body from weight loss.

Modern weight loss drugs act by mimicking gut hormones that send a satiety signal to the brain. They do help to reduce appetite, but they are not suitable for everyone: they cause side effects in some people and the weight often returns after the course is stopped.

However, new research in the field of neuroscience and metabolism gives hope: perhaps future therapies will be able to "muffle" the brain signals that cause the body to return to its previous weight, even after the end of treatment.

Scientists also emphasise that health does not always equal "ideal weight". Even if the numbers on the scale change little, regular exercise, adequate sleep, a balanced diet and psycho-emotional well-being significantly improve heart health and metabolism.

Obesity is not an individual problem, but a systemic one. Combating it requires a comprehensive approach: improving school meals, limiting fast food advertising to children, creating walking and cycling zones, and controlling portion sizes in restaurants.

Research shows that it is especially important to target the early stages of life, from pregnancy to age 7, when the appetite and metabolic regulatory system is being formed. Parental nutrition, breastfeeding and habits during childhood can influence how the brain will regulate hunger and fat storage in the future.

The scientists' main point: obesity is not a personal failure, but a biological condition shaped by the brain, genes and lifestyle. But through science, medicine and smart policy, it is possible to change the rules of this "game" and help people stay healthy without guilt.