During fasting, the body gradually adapts its metabolism to a lower availability of nutrients. Its use of glucose declines, while the mobilization of fat reserves increases, and the fatty acids released become an important source of energy. At the same time, the liver steps up its production of ketone bodies, which various tissues can use as fuel.
In this context, autophagy is also enhanced. Autophagy is a natural mechanism of cellular maintenance and recycling: cells identify and break down damaged, aged, or unnecessary components, whose building blocks can be reused to obtain energy or to build new cellular structures.
Autophagy does not work like a switch that turns on the moment fasting begins. It is a continuous process of cellular maintenance that intensifies when nutrient availability falls and certain metabolic signals are activated.
Experimental research has shown that nutrient restriction and certain forms of fasting can stimulate autophagy. This mechanism has been linked to a better response to cellular stress and to processes involved in maintaining cellular and metabolic function. Its possible contribution to healthier ageing and to the prevention of some age-related diseases is also being investigated. In humans, however, we still lack sufficient evidence to claim that intermittent fasting prolongs life or rejuvenates the body through autophagy.
Autophagy, moreover, is not exclusive to fasting. Physical exercise and caloric restriction can also modulate this process, which is part of the body’s usual mechanisms of cellular maintenance.
The aim of fasting is not to “cleanse” the body, but to temporarily modify the metabolic signals that regulate how cells obtain energy and maintain their components.
Intermittent fasting should therefore be understood as a nutritional strategy that may be useful for some people, but whose benefits also depend on overall diet, physical activity, sleep, and metabolic state. It is not suitable for everyone and, in certain circumstances, requires medical assessment and supervision.
Eat little, in few meals—but eat well!
Today’s research is tomorrow’s therapy