First, we’ll talk about what Intermittent Fasting “looks like” in real life, then discuss how and why it works.
What is Intermittent Fasting?
Intermittent Fasting describes a practice whereby one limits the time during which they eat, and “fasts” the rest of the day. For autophagy (cellular cleanup), weight loss, and resetting insulin sensitivity, the ideal length of an intermittent fast seems to be 14-18 hours. For instance, a person might decide to eat only between the hours of noon and 6:00 PM, and fast from 6:00 PM until noon the next day (18 hours).
There is no magic in the 6:00 PM to noon time frame. ANY 14-18 hour stretch of time during the day would work equally well. One could decide to eat between 6:00 AM and 4:00 PM, and fast from 4:00 PM until 6:00 AM the next day. That would be a 14 hour fast and would work similarly. There is some evidence that 16 hours of fasting is the magic number. So in that case, we could take the above example and change it slightly so that all eating was done between 6:00 AM and 2:00 PM. By fasting from 2:00 PM until 6:00 AM the next day, one could accomplish a 16 hour fast.
By fasting, what we mean is no “significant” caloric intake. Non-caloric drinks are not included in the fast. In fact, it’s just as effective and probably safer to plan to drink water during the fast. Black, non-sweetened coffee and unsweet tea are also perfectly acceptable.
Moreover, it’s not required to fast every single day. 90% of the benefits of fasting can be accomplished by fasting only 2-3 days per week and eating the way you normally would otherwise.
So, fasting for 14-18 hours (ideally at least 16 hours) 2 to 3 times per week, while still drinking water or other no-calorie drinks doesn’t sound so tough, right?
How Does Intermittent Fasting Work?
While human studies are scarce, much of the most recent evidence supports the idea that IF has benefits over and above that of simple caloric restriction for weight loss. Specifically, this study indicates that insulin resistance/sensitivity, blood pressure, and oxidative stress can all be improved. While the mechanism is debatable, it seems clear that autophagy and reduction in insulin resistance play a significant role.
The term autophagy refers to our bodies’ innate ability to rid itself of damaged and dying cellular constituents. This is not to be confused with apoptosis, which refers to the programmed death of entire cells. Autophagy, on the other hand, is a repair mechanism by which cells are able to renew and heal themselves. This process seems to be up-regulated by Intermittent Fasting, likely due to the fact that the body responds to this mild stress by “cleaning up” and becoming more efficient.
Insulin Resistance occurs when the pancreas is persistently and consistently subjected to a high blood glucose environment. By practicing Intermittent Fasting, we are able to decrease blood glucose and give the pancreas a break from this constant stimulation. This allows the pancreas to rest and “reset” thereby improving Insulin Sensitivity and diabetes control.