He is a world renowned cell biologist known for his studies on the role of fasting.
He is an expert on nutrient response genes. In particular, their action on cellular protection, aging and diseases (1)
Prof.Longo noted that during a fast, the white cell count dropped quickly.
Once the fast ended, and refeeding began, the white blood cell count rapidly climbed. This caused Prof. Longo to wonder where the new cells came from.
He found that Prolonged fasting (PF) lasting 48–120 hours reduces pro-growth signaling. A fast also activates pathways that enhance cellular resistance to toxins and stress in mice and humans (2)
Further, he found that:
“The physiological changes caused by PF are much more pronounced than those caused by calorie restriction or overnight fast”.
There is no doubt and overwhelming evidence that fasting is super healthy.
Fasting has been well researched and the results prove that it has multiple health benefits.
When you take a break from food the body is triggered into flicking the switch on stem cells. This causes them to ramp up the production of new white blood cells.
These are the important cells that fight off infection. With new healthy white blood cells, your immune system will be working at its best.
With the immune system renewed, we are going to maximize our chances of living not just a long life, but a healthy life too.
Why fast for 72 hours and not less?
Various cool and healthy things happen to your body when you fast, but at different rates.
A fast as short as 12 hours will get you using your glycogen stores. You probably won’t be in ketosis at this stage. Most people have enough glycogen stored to run on zero food for longer than 12 hours.
Therefore, unless you’ve been very low carb before your fast, 12 hours is good for you, but ketosis is not guaranteed.
This study found that there is a point of negative energy balance at which liver glycogen stores are depleted. At this time, fatty acids are mobilized.
This is the point at which ketosis starts and it is typically beyond 12 hours after the start of the fast.
Between 12 and 24 hours is when the real business of ketone production takes off.
At this stage, most people will have burned through their glycogen stores. The body will have switched over to burning fat for fuel.
At 48 hours, this study found that the first response to food restriction which was observed at 24 hours, was a significant increase in the number of autophagosomes.
The presence of these indicates that autophagy is well under way.
This is because it is autophagosomes which fuse with or digest cellular constituents during autophagy.
This process can be seen at 24 hours without food, but was magnified after 48 hours of fasting.
A few hours later, at 54 hours and the benefits of fasting are even stronger. Your insulin levels will have fallen to their lowest level since you started fasting.
Further, your body is increasingly sensitive to insulin (Klein et al., 1993).
72 hours fast will give you all the benefits
It’s been found that at 72 hours, you’ll be really reaping all the benefits that fasting and autophagy can bring.
Once you have fasted for 72 hours you will be feeling the all cognitive benefits. You will have more focus and will be able to think clearly.
This would have served you well in the days when humans regularly faced a lack of food.
At a time you needed to hunt for more food, you would have needed to be calm and thinking clearly. Focus would have been required if you were to find your next meal.
Importantly, at 72 hours you have been fasting long enough for a breakdown of old or damaged immune cells. This leads to the regeneration of new ones.
Your entire immune system can be reset, with multiple health benefits.
Prolonged fasting up to 72 hours promotes growth in almost all cells.
This study showed that a long fast of 72 hours was able to protect cancer patients against toxicity, when done immediately before they began chemotherapy.
How many times do you need to do a 72-hour fast?
There needs to be more research about how often you need to do a 72-hour fast to optimize your health.
However, several scientists including Prof Longo have suggested you needn’t do this too often. There seems to be no need to do a fast of this length more often than two or three times a year.
There are many fans that do embark on this fast much more often. Keto dieters often do a 72-hour fast each month or so.
However, it’s important to remember that too much autophagy can be damaging, so more is not better when it comes to fasting.
It’s also necessary to take into account your weight, fat percentage and health. Some people can tolerate a 72-hour fast more easily than others.