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Is fasting good for your health?


Fasting involves abstaining from food (and often drink) for a period of time. There are different types of fasting, including partial fasting, intermittent fasting, prolonged fasting and even complete fasting. Each of these fasting techniques has its own specific features, sometimes dictated by strict rules (in the case of religions) or more flexible rules (based on the particular school of thought). However, one thing is certain: fasting places stress on the body. Here is an overview of the different stages of fasting and the effects on the body.   

What are the different stages of fasting?

From a medical point of view, the fasting period starts from the sixth hour after the last food eaten, even if the body continues to metabolise normally during the first day of fasting. During these first 24 hours, the body uses blood glucose or glycogen from the liver as alternative sources of energy until these stores run out.

From the second day – and up to five to six days – the sources of glucose are mainly amino acids (molecules that are the building blocks of proteins) and, to a lesser extent, sodium lactate (salt molecules) and glycerol (alcohol molecules naturally present in the body).

From the fifth or sixth day, the liver and kidneys produce ketone bodies, which are alternative fuels for the body made from the breakdown of fats. The brain uses these substances when glucose is in short supply. Ketones suppress appetite and reduce feelings of hunger.  

What are the dangers of fasting?

Fasting is particularly dangerous for people who have a medical condition or those with poor health. The body is ultimately in a state of stress and fasting places even more strain on it. The body will begin to consume protein mass and directly attack its own muscles to provide itself with protein. For this reason, fasting is particularly dangerous for people who are already thin as well as pregnant women and the elderly.

If your goal is to lose weight, fasting is not the answer. Going without food will automatically lead to weight loss at first, but your body will then put in place compensation strategies, which will directly result in rapid weight gain after the fasting period. You may even end up gaining more weight than you lost.

From a scientific point of view, no study has yet been able to demonstrate that fasting is good for your health, whether in terms of detoxifying the body, controlling weight, cleansing organs or resting the body. The body naturally produces energy, keeping what is good for it and rejecting what is bad.      

What should you do if you want to start fasting?

Although fasting does not provide any obvious health benefits and may cause harmful effects on the body, it could be recommended in the future in specific situations, such as in chemotherapy for cancer treatment. However, if you do want to start fasting, please speak to a nutritionist first. He or she will be able to provide advice about the best fasting technique for you. The nutrition unit at Hôpital de La Tour is always available to answer any questions or concerns you may have.