Fasting, or the purposeful restriction of food intake, has been practiced for millennia both for religious reason as well as health reasons. People who fast for religious reasons do so either as a means to achieve a different religious consciousness, or as a means of atonement, as Catholics do during Lent. But for our purposes, there is evidence that fasting has a multitude of health benefits, whether practiced as a short term, mild fast, or as a long-term strategy of calorie restriction. On the far end of the spectrum is extreme calorie restriction and the jury is still out on whether this extreme measure will provide greater longevity.
There is a great quote from Science Magazine, "Eating shortens life…"  It goes on to explain that calorie restriction, by as much as 40% increases longevity in organisms and fends off diseases like cancer, heart disease and diabetes. Studies in monkeys, meant to test the efficacy of calorie restriction in monkeys  don’t agree that the monkeys will live longer, but do agree that they maintain health for a greater portion of their lives, known as healthspan.
If you are like me, you might be thinking, "What’s the use of a longer life if I have to pay for it by not enjoying life through wonderful food?” I personally love food. Lucky, there are alternatives. So what happens when you give your body a break from the task of eating, digesting, and processing all that food and resultant waste products? Quite a few things actually. Your body, during periods of abstinence first of all adjusts your hormones to make body fat more accessible. Yes, the whole idea of calorie restricted dieting was about allowing our bodies to go into increased ketosis, or a fat burning cycle where ketones are released. This also happens in low carb diets, and unfortunately for diabetics it’s a sign they aren’t using enough insulin. Speaking of insulin, in healthy people, short term fasting lowers the amount of insulin in the blood which also assists fat burning.
Our bodies naturally make human growth hormone (HGH), and this amount increases by as much as 5 times during fasting. HGH has a number of health benefits and also aids in fat burning. HGH is also known to build muscle mass. As we age, and lose muscle mass, this can be a strategy to reduce or reverse that trend.
Because we’re smart and targeting the diseases most likely to kill us, you’ll be happy to know that intermittent fasting fights heart disease in many ways. First of all, you can lose as much as 8% of your fat in 3 to 24 weeks through intermittent fasting.  Additionally, it can reduce blood pressure, lower cholesterol, both LDL and overall cholesterol, lowers blood sugar and reduces inflammation.
"The first randomized study, the 2-year CALERIE trial, wrapped up earlier this year. Ravussin, who is one of the trial's leaders, says that the final results haven't been analyzed, but in 2011, he and a colleague revealed that 6 months of calorie cutting reduced the participants' risk of cardiovascular disease by 28%." Science Magazine 2012
When the body gets a rest from the eat/digest cycle it enters a period of something called autophagy. According to Wikipedia, “Autophagy allows the orderly degradation and recycling of cellular components.” Basically, our cells go through a cycle of repair and removal of waste products. They clean house.
Warning: Autophagy is known to assist the growth of cancer cells. And in fact, restricting autophagy during cancer treatment has been shown to enhance the effectiveness of cancer therapies. Make sure you speak with your doctor before beginning calorie restriction.
Another part of our body that undergoes changes during fasting is in the microflora living in our gut, or microbiome. Intermittent fasting has been showing to be helpful in creating a better balance between the good bacteria and the bad bacteria. This “bad bacteria” has been shown to be an early cause of colo-rectal cancer.
Types of fasting
The simplest type of fasting is to restrict the hours during which you eat. This is common in the Muslim community during the period known as Ramadan, where they fast during the period from sunrise to sunset.
Intermittent fasting, or fasting on certain days by restricting what you eat by as much as 75% has been shown to be as effective as calorie restriction, or eating very little every day. During the fast period, you don’t have to deprive yourself. Instead, switch to eating healthy things like nuts, avocados, and natural fats like coconut oil and even butter. Just try to stay away from breads, pasta and other carbs during your fasting period.
Alternate Day fasting is a type of intermittent fasting where you fast one day and eat unrestricted the next. In many studies, no form of intermittent fasting has really proven to be better than another. It’s more of what you are willing to do.
What About Hunger?
According to one of the definitions in the Merriam-Webster dictionary, hunger is “an uncomfortable feeling in your stomach that is caused by the need for food” In fact, a lot of hunger has to do with our addiction to sugar, whether directly in the form of sugar or the sugar we get from processing carbohydrates found in breads, pastas, potatoes, and rice. Over time the body gets over this addiction to sugar and the cravings stop. It won’t be overnight. It might take as long as several weeks to completely be free of these cravings.
Summing it all up
While several animal studies have shown that calorie restriction has had nothing short of miraculous results in longevity in mice, worms and other small animals, the same result has been less than exciting in mammals. But what is true is that fasting causes us to lose weight, one of the major sources of negative impact on our health. Additionally our bodies pump out chemicals like HGH that support an increase in muscle mass. Our metabolisms go up and our cells clean themselves out. We lower stress hormones and inflammation and reports show that we can reduce the incidence of cardiovascular disease and cancer by supporting our microbiome through fasting. See a health professional before beginning a fast, or a period of calorie restriction to make sure you are healthy enough to go on a fast, and have them help you design which type of fast might be right for you.As always, live longer,
- Nature. 2012 Nov 8;491(7423):254-8. doi: 10.1038/nature11465, Adenoma-linked barrier defects and microbial products drive IL-23/IL-17-mediated tumour growth, Grivennikov SI1, Wang K, Mucida D, Stewart CA, Schnabl B, Jauch D, Taniguchi K, Yu GY, Osterreicher CH, Hung KE, Datz C, Feng Y, Fearon ER, Oukka M, Tessarollo L, Coppola V, Yarovinsky F, Cheroutre H, Eckmann L, Trinchieri G, Karin M.