The Truth About Fasting

The benefits of fasting have been big news lately. But how effective is it? Most people are interested in it as a weight loss tool, and indeed you can lose weight using it, but in reality it has many benefits beyond weight loss, and some of them are quite miraculous. It has been known for many years that it extends the life of mice, worms and flies rather dramatically, and even appears to extend the life of monkeys. Does it extend the life of humans? Many people are convinced that it does, but the truth is that we’re still not sure, although it looks hopeful. There’s no doubt, however, that it has health benefits in relation to heart disease, cancer, dementia, and even your mood and well-being. It can’t be called a cure, but it does set the stage for healing by allowing vital parts of your body to rest and recuperate. There’s no doubt that excess eating puts a burden on your body, and that it needs an occasional rest. Indeed, studies have shown that if it doesn’t rest, it forgoes much of the repair and regeneration needed for optimal health.

Glucose, Glycogen and Fat

Your body needs energy to run properly, and it gets this energy from the food you eat. Food is turned a form of sugar called glucose. Your cells (and particularly the ones in your brain) need a constant supply of glucose, and if it gets low you begin to feel fatigued and weak.

Glucose circulates in your blood after you eat, and it is used up fairly rapidly as you go about your everyday tasks. If not replenished, it is, in fact, depleted in a few hours. This creates a problem: how do you maintain a good supply? Glucose itself can’t be stored, but it can be turned into a form called glycogen that can be stored in your muscles and liver. From here it can be drawn out and used as needed. It is usually good for about 10 to 12 hours.

What happens when it is depleted? The body then turns to the fat cells that are stored throughout your body. They can be broken down and converted to what is called ketones. This is, of course, what dieters look for, namely, the loss of fat cells. But you have to be careful if you remain in this stage for too long. The body soon begins to break down protein; it can also be converted to glucose through a rather complicated process. And this causes the loss of muscle – something you don’t want. Indeed, in most diets, a fair amount of the weight loss comes from muscle loss along with depletion of water (leaving you dehydrated). So don’t be deceived.

Weight Loss Through Fasting

As I mentioned earlier, you can lose weight by fasting, but most doctors and dieticians do not recommend long fasting periods because they can have an adverse effect on your overall health. In addition, it is difficult for most people to fast for long periods of time. A better alternative is what is called intermittent fasting in which you fast on certain days of the week, and eat normally on the others. One form of this is alternate-day fasting. In this case you fast (or restrict your calories) on one day and eat normally the next. This works well for some people but Dr. Michael Mosley of BBC has put forward what he calls the 5-2 fasting diet. In this diet you restrict your calories only two days a week. He suggests 500 calories for women on these days and 600 for men. This is much easier for most people to do, and it appears to give the same results as more extended fasts. But weight loss is not the most important benefit of such a diet, so let’s look at the other benefits.

Health Benefits of Intermittent Fasting

It may be hard to believe but there are tremendous benefits to intermittent fasting. The main thing it does is rest many of the vital parts and organs of your body so they can do their job better. Some of these are:

  • It rests the digestive system. This, in turn, helps many other parts of the body.
  • It reduces blood sugar. This decreases the production of insulin, and makes it more sensitive and effective. Furthermore, it rests the pancreas.
  • High blood pressure is controlled.
  • Detoxification occurs. Fasting helps clear out your body and detoxify it. For this it is important to drink lots of water.
  • It increases your energy and makes you feel better.
  • It helps protect you against heart disease and stroke.
  • It helps rev up your immune system and as a result it fights excess (of chronic) inflammation.
  • It reduces oxidative stress caused by free radicals in your cells.

Some Surprising and Different Benefits

One of the hormones in your body is called IGF-1 (insulin-like growth factor 1); it helps your cells grow and is particularly important in growing children. As you reach adulthood, however, it decreases significantly. This is important, since as you grow older it appears to have adverse effects: it accelerates aging and can even lead to cancer. So it’s not something you want high levels of when you’re older. And studies have shown that intermittent fasting decreases it.

Also, in your brain is a protein referred to as BDNF (brain-derived neurotrophic factor). It is important because it has been shown to help stem cells turn into new neurons. This takes place in a section of the brain called the hippocampus, which is critical in relation to memory and learning, BDNF has many effects: it appears to protect against dementia and Alzheimer’s disease, and it also acts as an anti-depressant, suppressing anxiety.

Finally, intermittent fasting also helps increase autophagy, which is a system in the cells that gets rid of damaged molecules that could lead to serious neurological diseases.


Diabetes comes in two forms: diabetes I and diabetes II. We will be mainly concerned with diabetes II. As we saw earlier, all cells use glucose as fuel. But it can’t get into the cells without insulin. Insulin is produced in the pancreas according to the amount of glucose in the blood; it’s role is to allow the glucose to enter the cell. Most of the cells in your body have what are called insulin receptors that bind to insulin that is circulating in your blood. When a cell has insulin attached to its surface it allows glucose in, so it obviously plays an important role in your body. But too much can be detrimental. Insulin increases your hunger, promotes the storage of fat cells, and it has been linked to diabetes and heart problems.

One of the major problems associated with insulin is what is called insulin resistance. In this case the pancreas produces insulin, but insulin receptors on the cells no longer work properly, and don’t allow glucose to enter as they should. With no place to go, the glucose continues to circulate in the blood, and the cells soon begin to starve. The body realizes that something is wrong and the pancreas produces more insulin in an attempt to get sucrose into the cells, but this causes the pancreas to overwork, and it eventually begins to wear out. The result is diabetes II.

Studies have shown that intermittent fasting improves your insulin sensitivity. This in turn allows your body to do a better job of controlling your blood glucose levels after meals, and therefore helps rest your pancreas. Both of these are important in relation to the prevention of diabetes II.

Rules for Fasting

  • It is best to use a 5 – 2 approach, with regular meals 5 days a week, and two days of restricted food (500 calories for women, 600 for men).
  • Stay hydrated. Drink Plenty of water; it helps flush out toxins.
  • When not on fasting days (and even when fasting), keep your nutrition maximized. In particular, eat sufficient vegetables, fruits and whole grains.
  • Remember that 12 hours of fasting is needed for the effect. From 12 to 18 hours is best. It plateau’s beyond 18.
  • You can exercise during fasting periods, but don’t overdo it.
  • Be careful of fasting if you are diabetic.

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