On a previous post, I discussed how it is important not to eat too little, as then the body goes into emergency mode and slows down the metabolism.

Then why am I now writing a post about fasting? Seems counter-intuitive, isn’t it? Wouldn’t fasting cause the body to spend as little energy as possible?

There’s no simple answer. Unless the fasting person works out vigorously, they will lose muscle tissues as well as fat, and this could lead to a decreased metabolism. Eventually, they will have to stop fasting, and then they’ll gain everything back again, including some additional extra pounds due to the slower metabolism. However, this happens only in prolonged fasting. Intermittent fasting can actually have very positive impacts on our bodies.

I’ve read the very interesting book The FastDiet written by Michael Mosley. In the book, Dr. Mosley discusses a very interesting study conducted by the Salk Institute for Biological Studies. In the study, the researchers 2 groups of mice and fed them a high-fat diet. All the mice got the exact same amount of food, the only difference being that the mice in group one were allowed to eat whenever they wanted, while the mice in group two had to eat their food within an 8 hour time period. This meant that there were 16 hours of the day in which they were fasting. After 100 days, the mice from group one, who ate whenever they wanted, had developed high cholesterol and high blood glucose and had liver damage. The mice from group two, who had to fast for 16 hours a day, put on far less weight (28%) less and suffered much less liver damage, despite having eaten the exact same amount and type of food. They also had lower levels of chronic inflammation, which suggests they had reduced risks of heart disease, cancer, stroke, and Alzheimer’s. The researchers explained that when you’re eating, your insulin levels are elevated and your body is stuck in a fat-storing mode. Only after a few hours of fasting is your body able to turn off the fat-storing and turn on the fat-burning mechanisms.

Other research found that Human growth hormone (HGH) goes up during fasting. This hormone aids in increasing muscle tissue gain and decreasing fat. Two other studies found that fasting for about 2 days increase metabolism by 3.6%-14%, however, fasting for more than 2 days can slow down the metabolism rate.

The scientific evidence sound convincing, and it’s no wonder that intermittent fasting  diets are becoming more and more popular.

There are several common methods for intermittent fasting, with the most common one being the 5:2 diet (the Fast Diet) which is recommended by Dr. Mosley. It involves eating regularly for 5 days, and for the other two days of the week eat only 500-600 calories per day, making sure to eat foods that have a glycemic index less than 50. You can read more on the glycemic index here.

There are other ways to do intermittent fasting, for example, eat-stop-eat method which involves fasting for 24 hours once or twice a week. Another popular one is the 16/8 method, in which you fast for 16 hours and eat for 8 hours each day. The Alternate Day fasting proposes fasting every other day.

If you are interested in fasting, I recommend buying The FastDiet, it includes a lot of good information and tips on how to succeed in such a diet.