Fasting is often described as a way to “detox” or “cleanse” the body.
The idea sounds simple: stop eating for a period of time and give the body a chance to remove accumulated toxins.
But this is not how the body’s natural detoxification systems work.
The body already has its own detoxification systems
The body continuously processes and removes waste products and potentially harmful substances.
The liver breaks down and processes many substances so they can be safely eliminated. The kidneys filter the blood and remove waste products through urine. The lungs and digestive system also play important roles.
These processes happen continuously. They do not need fasting to switch them on.
Research examining popular detox diets has found little clinical evidence that these programs remove toxins from the body.
Fasting does change the way the body uses energy
This does not mean that fasting has no biological effects.
After a period without food, insulin levels fall and the body begins to rely more on stored energy. Fat breakdown increases and the liver can produce ketones, which the body can use as an alternative source of energy.
This is a normal metabolic response to not eating.
It is also important not to confuse this normal production of ketones with diabetic ketoacidosis. Diabetic ketoacidosis is a dangerous medical condition, usually associated with severe insulin deficiency. It is very different from the normal metabolic changes that can occur during fasting.
Can fasting still be relevant to healthy aging?
Yes — but not because it “cleanses” the body.
Studies of time-restricted eating suggest that it may help with weight control and some aspects of metabolic health, including blood sugar regulation. Maintaining a healthy weight and good metabolic health is important for long-term health and healthy aging.
Other possible effects of fasting on cellular processes involved in aging are also being studied, but they should not be confused with detoxification.
