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by Rahul Kapur
Fasting is an age-old practice that is found in many traditions throughout the world. It is the complete abstinence or reduction of calories for a certain period of time. In medical terms fasting is known as total caloric desistance (TCD). There are several subsets of TCD that include intermittent fasting, alternate-day fasting (ADF), routine periodic fasting, or intermittent energy restriction. All of these forms of TCD include windows of fasting and feeding which are separated by some amount of time.
Intermittent fasting has recently gained popularity among mainstream diet and weight-loss circles. Practitioners claim that it can lead to positive weight changes, metabolic effects, and overall health. In order to better understand these claims it is important to examine the practice of intermittent fasting and its physical and physiological effects on the body.
There are several types of intermittent fasting, such as time-restricted fasting, which is simply not eating between dinner and breakfast the next day. The fast duration is usually around 10-14 hours and it is done daily. Another type is called the 16/8 method, which involves fasting for 16 hours each day. Similarly there is the 5:2 diet, which is the consumption of 500-600 calories on two nonconsecutive days and normal eating the other 5 days. Essentially, all of these methods reduce calorie intake for some period of time throughout a day or week. Proponents say that any of these methods can achieve weight loss as long as food intake during non-fasting days is regular. In other words, compensating for calorie reduction during a fast by overeating during eating periods can have a negative effect on weight loss.
Based off of one study, fasting can have many effects on the body and more specifically, cells and hormones. For example, it can enhance growth hormone (GH) secretion as much as 5-fold in the human body. This may play a vital role in switching from glucose to fat as a fuel source for cells, leading to fat loss.
Fasting can also increase sensitivity to insulin, according to a study published in American Journal of Clinical Nutrition. Researchers took 16 nonobese subjects and measured metabolic markers for an intermittent fast for 22 days. They noticed that levels of stored insulin levels dropped dramatically, which makes fat more accessible to burn.
Evidence suggests that fasting can help cells undergo autophagy. This is a natural process wherein cells recycle their degraded components as a way to maintain health and function. This an important step in demonstrating why fasting can be an important and even vital practice for human beings.
Researchers have also demonstrated that intermittent fasting and caloric restriction can have a role in anti-aging by increasing signals that lead to protecting brain function and increasing antioxidant production. This leads to better coping mechanisms for cellular stress and increased disease resistance.
In terms of weight loss, scientists have shown that intermittent fasting is equally as effective as calorie restriction for losing weight and increasing protective factors against diabetes mellitus (DM) type 2. One such factor is belly fat. It is shown that increased excess fat around the waste is a risk factor for type 2 DM. In a study conducted in 2014, it was reported that subjects who underwent intermittent fasting from 3-24 weeks lost 4-7% of this harmful belly fat, decreasing the risk for DM and providing protection against other ailments such as heart disease.
Critics of intermittent fasting will say that more testing and human study needs to be done to really understand the effects it can have on human health. As of today, clinicians will have little research-oriented basis to offer fasting for patients simply because most research done so far has only been conducted on animals. Intermittent fasting and caloric restriction in general, may not be a cure-all, but the current data suggests that it deserves greater attention in clinical circles as a viable tool for generating optimal health for prevention and treatment of disease.
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by Khyati Kapur