In the world of nutrition and health, it is very common for a new diet, a new method or a new “miraculous cure” to appear almost every day. Apart from being rationally skeptical of any kind of definitive cure for anything, I think we should be able to overcome the ever-present ad novitatem fallacy (the idea of something being better or superior just because it is new) and look to the past –as well as to the present- for answers.\nA good example of past traditions being useful in the way we conceive health is the revival of fasting, a practice that goes back in a medical context to the father of modern medicine himself, Hippocrates. Even though it has been present as part of our lives as humans in almost every culture and religion for millennia, fasting (more specifically intermittent fasting) has made a comeback since 2012 with the help of doctors such as Michael Mosley, Jason Fung, and journalist Kate Harrison, among others.\nBut what is intermittent fasting? In a nutshell it consists of the voluntary abstinence of food for certain periods, be it hours or even days. The main objective of the fast is to deprive the body of glucose, so that it turns to other sources of energy such as glycogen (excess glucose stored in the liver) and fat, the last functioning as the long term food energy storage. This not only helps the body to burn said fat and lower insulin levels, but also produces other many benefits, depending on the fasting regime you are following.\nOne is the production of ketone bodies, which is one of the products of said breakdown of fat stores (called triglycerides); ketones can then be used to supply approximately 75% of the brain’s energy needs, as they are capable of crossing the blood brain barrier (a thing that not all forms of fat can do). Another positive is that not only do the insulin levels go down -and blood glucose too, in a span as short as 24 hours- but regular fasting, by routinely lowering insulin levels, can improve insulin sensitivity; this is very important because the main factor driving type-2 diabetes is insulin resistance, and regular fasting can help significantly with this.\nAnother byproduct of this is that fasting rids the body of excess salt and water, as insulin causes salt and water retention in the kidney; this in turn helps to reduce blood pressure slightly, while decreasing LDL-cholesterol and triglyceride levels. It is also beneficial for losing weight, first by producing results that are almost twice as better as those of bariatric surgery patients. But even in studies comparing fasting approaches to caloric restricted diets, the fasting groups not only lost more weight generally, but lost twice as much of the dangerous visceral fat.\nTalking about cancer, fasting provides many benefits. It lowers the activity of IGF-1, a hormone associated with cell proliferation in many cancers; it also lowers pro-inflammatory cytokines like IL-1β and IL-6, both known cancer promoters. On the other hand it promotes mechanisms in our body that can help fight cancer, like limiting cell growth and proliferation, or promoting autophagy, a process where damaged or inefficient cells are sacrificed for economizing purposes, including the dysfunctional mitochondria in cancer cells.\nFinally, it can improve your cognitive readiness. When you eat, blood goes to your digestive system to deal with the great influx of food, leaving less blood for brain function, this helps to explain why you may feel sleepy and not very alert after eating large meals; fasting does precisely the opposite, allocating more blood to your brain.\nNow we know that fasting has been around for many millennia for a reason, not only as a significant part of religious rituals, but because it has many benefits for our health, of which the ones shown before are just only one part of the picture of what this practice can do for us. Of course, as always, if you have found this could be an option that seems suitable for you, we encourage you to start with the assistance and guidance of a nutritional expert or a physician. In the following articles we will expand on this subject, tackling common myths surrounding this practice and the best ways to start.