Don't you hate it when you ask a simple question, and just can't get a straight answer? A "yes or no question" deserves an up or down vote: yes ... or ... no.
Unfortunately, if you were to ask me if fasting is good for you or not, I wouldn't be able to give you a simple answer. Yes, it can be bad for you but, yes, it can also be good for you. Sorry about that.
THE EMOTIONAL CONTEXT OF FASTING
What's interesting about the question itself is that the answer has little to do with the number of calories you eat during the fast, whether you're going vegetarian or vegan or just hitting the Lenten fish fry Fridays.
What makes fasting good or bad or indifferent to your health has more to do with the emotional context in which it is performed. In this case, the mind matters.
The Good of Fasting
If this sounds weird to you, all I can do is trot out the data, so let's just start with the general basics of calorie restriction. Benjamin Franklin was correct when we stated that "To lengthen thy life, lessen thy meals." In fact, cutting calories is the best way to increase longevity, and the age related deterioration that happens as your brain gets older. So at the most basic level, curtailing calories helps your body and brain.
Ah, I see. Fasting is a good thing.
The Bad of Fasting
However ... if you just go cold turkey and severely clamp down on calories, your body will interpret the situation as a stressor. Your systems can go into what is commonly called the "starvation mode", in which your metabolism slows down (you're burning less fuel). Even worse, your body tends to hold on to the fat it does have, essentially frustrating the very point of the fast in the first place.
And then, after that dietary fasting fiasco, there's the very real risk that you will come off the fast by consuming too much, in a binge-like compensation for your prior deprivations. This, in turn, can lead you into a very unhealthy weight cycling that can help contribute to metabolic syndrome, among other biological nastiness.
Ah, I see. Fasting is a bad thing.
The Pretty Side of Fasting
However ... research on religious fasting practices shows that individuals who engage in voluntary, controlled caloric restriction in the context of this kind of structured practice do not suffer the bad side effects of fasting, which can occur if you just turn off the food spigot.
For example, in the Ramadan fasting tradition, they fast during the day and then have "iftar", which is the evening meal. This intermittent fasting practice will last for 28 - 30 days. Under these conditions, voluntary food restriction produces improved immune systems, less chronic inflammation, and better cholesterol to boot.
In the Orthodox Christian tradition, they revert to a near vegan dietary regime during one of several fasts throughout the year, lasting from 15 to 48 days. The rules for their many varieties of the fast vary, but include some form of voluntary restriction for extended periods of the day (from evening to 3pm the next day, in one example).
Some of the more favorable effects of these fasts include the lowering of body mass, improved insulin control, total cholesterol, and an improved between the bad cholesterol (LDL) and the good cholesterol (HDL).
Ah, I see. Fasting is a very good thing.
HEALTHY THOUGHTS MAKE HEALTHY FASTS
What makes your fast slip from the "bad for you" category to the "good for you category" comes down to how your body interprets the context. It's not about the calories-in-calories-out model; it's not about the molecule micromanagement; and it's not about the religion per se.
Healthy fasting occurs when your brain creates the context of a spiritual, emotional, or physical cleansing. That's because "not eating" is not interpreted as a punishment (whether externally imposed by some arbitrary program OR internally imposed as a deprivation diet). It's taken by your mind - and so your body - as a means to a healthier end.
So, what's the bottom line? Fasting is not good for you. And fasting is not bad for you. Not on its own; not until you make it that way by HOW you do it. If you use fasting as a draconian diet technique to lose weight and punish yourself for your past dietary sins, or whatever, your body will work against your very efforts.
On the other hand, if you use fasting as a part of a meditative, purposeful cleansing of the body, mind, and spirit, it will be taken that way. In this way, the above data provide some degree of truth to the phrase that we create our own reality.
"Diet" is more than just what you put in your mouth, it's also the context of that consumption. In the same way, "fasting" is not the absence of eating. It is the presence of a process of internal cleansing. Taken within this context, the fast is a very healthy thing to do.
Ah, I see. Fasting is neither bad nor good, but it is we who make it so.
Dr. Will Clower is an award winning author, media personality, and CEO of Mediterranean Wellness