Your body is not meant to fast; there is a difference between the body benefiting from stress and from coping with stress. I know fasting is popular with numerous longtime posters in here, but I will again strongly voice my opposition to its recommendation, and that the majority of the science investigating the matter I've reviewed clearly indicates that it's not healthy. In fact, they've found an increase in the probability of unfavorable genetic-line mutations amongst individuals descended from populations that experienced extended periods of fasting (aka starvation). That means that people who have experienced starvation are more likely to have children with inferior physiology (ex. more prone to cancer).
I know what the pro-fasters will say. "Fasting isn't starvation." Well, yeah, it is. It's just starvation in a shorter time frame.
Alright, Christmas and finals are finished now so I can get back to wasting my time here. I feel I need to address this post especially since it's coming from a mod who a lot of people look at for advice.
First of all, likening starvation to intermittent fasting is absolutely ridiculous. It's the same as likening starvation to minor caloric restriction - and I don't think you can debate the body of evidence that's been built over the last 50 years in support of caloric restriction for increasing longevity and inhibiting a lot of disease mechanisms (namely diabetes, obesity and cancer). Intermittent fasting is relatively newer, but the results so far have been incredibly similar to caloric restriction. If you can find evidence contrary to that, I would like to see it. And no, those Scandinavian starvation papers do not count. Chronic starvation and intermittent fasting are apples and oranges.
I have stated in the past that the body works by absolute value. A blood pH 3 points above baseline is just as bad as blood pH three points below baseline. The same can be said for fasting-state mechanisms vs. growth mechanisms, or starvation vs. obesity.
Let's say you eat constantly, instigating growth factors and the cellular pathways they promote. Anyway you put it, constant eating will illicit a constant insulin response, among other growth factors. This in turn stimulates the IGF-1 pathways like Pl3 or AKT + mTor, a pathway that once initiated begins a positive feedback loop (meaning more growth stimulates more growth). This also happens to be a primary pathway in cancer development. This is due not only to the growth nature of the AKT/mTor pathway, but because the downstream molecules like PKA or CREB inhibit DNA repair mechanisms like FOXO, AMPk and tumor-inhibiting p53. FOXO, p53 and AMPk are inihibited during times of growth (feeding), and they are responsible for a plethora of necessary processes - DNA repair, neuronal stress resistance, programmed cell death, glucose metabolism, peroxisome based anti-oxidant activity - the list goes on. That being said, over-exposure to the FOXO, AMP and p53 is in itself dangerous since growth is a necessary part of cell maintenance - especially through mitotic division. If programmed cell death runs rampant, well, I think you know what happens. Again, this comes back to the point that both growth and reparative processes have to be kept in balance. Straying too far on either side is dangerous. Peroxisome over-regulation is dangerous, because the pH in peroxisomes can destroy cells in a non-controlled process. DNA repair mechanisms inhibit cell division and growth. The list goes on. Both sides can be dangerous, but both sides of the coin are
necessary.
Technicalities aside, the very notion that constant feeding is necessary or even good for you shows a severe lack of understanding on how nature creates robust systems. Variability is a requirement for robustness. Exposure to variable conditions has shaped evolutionary processes since the beginning of life. To remove variable conditions, whether in the form of disease, allergens or bacterial exposure (ie: bubble kids) or in the form of feeding and fasting periods is to rob the body of the conditions in which it evolved. Conditions that the body requires to operate properly. This was most astutely observed in the advent of zoos. It used to be thought that cancer only existed in humans, but once we started putting animals in zoos, allowing them to eat ad libitum and live to old ages without being picked off by predators, we started seeing cancer in animals. Remove natural variability and you remove natural cellular function. It's no doubt that with the access to constant food, and therefore exposure to constant cellular growth, we've seen an explosion in cancer among all ages in our population.
Here is a fantastic review article that discusses in much more detail the methods in which CR and IF behave the same way (and their differences), and how it impacts health and longevity. I only touched on a few mechanisms initiated by CR and IF, the paper explains quite a few others.
ScienceDirect - Ageing Research Reviews : Caloric restriction and intermittent fasting: Two potential diets for successful brain aging