Introduction to Intermittent Fasting – How, What, Benefits and Cautions

Skipping breakfast. Eating all you want five days out of the week, severely limiting calories or even not eating anything at all the other two. Limiting your eating hours to only 6 or 8 hours a day.

These are all various iterations of the popular intermittent fasting approach to eating. Intermittent Fasting (IF for short) has gained significant mainstream popularity lately as its benefits have become more widely known and appreciated. And the benefits of intermittent fasting are certainly worth taking note.

The concept of fasting is surely nothing new. Scientific studies on its benefits have been around since the 1940’s, it’s found in every major religion’s texts, and surely goes all the way back to the beginning of human existence when food wasn’t available 24 hours a day like it is now.

The idea that we need to eat many small meals all day long and never allow ourselves to feel hungry, commonly taught as the method to maintain a high metabolism, is quickly being put to rest as the benefits of increasing the duration between meals have become too many to ignore.

The Benefits – So what are these benefits that people are willing to significantly alter their eating patterns to achieve?

The overarching concept is that as the body has to spend less time and resources on the high energy tasks of digestion it has more capacity to focus on activities that benefit us in other ways. These include ridding the body of toxins as well as repairing and rebuilding tissues. In addition, the smart approach to fasting also puts the body in an ideal state to lose weight. All of these things have significant potential to increase potential and our ability to avoid disease.

Let’s look at these benefits in order.


Despite what many product manufacturers would have you believe, cleansing and detoxifying is something your body does all the time, and it is happening 24 hours a day. The millions of cellular processes that happen every day take their toll on individual cells, particularly on the mitochondria. Ideally, the body identifies these worn out cell parts and replaces them (a process commonly referred to as autophagy). This is a constant task.

While this process is automatic and ongoing, it can be significantly hindered by a poor diet, but can even be slowed by a healthy diet simply by the fact that when your body is digesting incoming food it decreases its cellular custodial duties. Giving your body time to focus solely on cellular repair can be incredibly beneficial for optimal cleansing. [To learn more about detoxing at a cellular level, check out The Secret Detox Program]

Interesting research has come out regarding the benefits of fasting on neuron centric diseases like Alzheimer’s and Huntington’s. As autophagy is increased during a fasting state rundown mitochondria and other cellular molecules are eliminated from the neurons.1 You can see the connection then between the increased detoxification abilities while fasting and a decreased aging process. This is deep cleansing in its truest form.

Hormone Regulation

The effects of fasting on hormones are multi-faceted. Fasting has a dramatic impact on human growth hormone levels. Increased HGH results in greater endurance with faster muscle repair and growth as well as a slowing of the aging process. One study showed that interval training while fasting increased HGH by 1300% in women and 2000% in men.2

Of interest to all of us is fasting’s effect on insulin levels. Insulin resistance – when cells essentially ignore insulin as it rings the door bell trying to deliver its package of energy (glucose) – is a primary contributing factor associated with nearly every chronic disease. Fasting, especially when combined with regular exercise, is one of the most effective ways of normalizing insulin sensitivity.

Leptin, the hormone that regulates fat storage as well as hunger signals, and ghrelin, another hormone that tells your brain the body is hungry, are also normalized by routine fasting.

Leptin is produced by fat cells and works by telling the brain to turn off hunger signals when body fat levels are sufficient for survival and reproduction. (Since fat is necessary for survival, leptin is part of the reason low-fat diets never work and usually only result in the dieter being hungry all the time.)

Interestingly, it’s been shown that overweight people have very high levels of leptin, yet few who struggle with weight will tell you they rarely feel hungry. The body is yelling at the brain to stop eating but the brain has become deaf to the signals. This happens by the same mechanism that leads to insulin resistance: consistent overexposure to high levels of the hormone.

Fasting, and in particular when combined with decreased sugar consumption, allows the brain to clean out its ears and properly hear leptin calling.

Weight Loss

The natural sugars in any meal that aren’t immediately needed for energy are stored in the liver as glycogen. When maximum glycogen storage has been achieved, the body then stores this energy as fat. Glycogen stores are the first fuel source the body will turn to for energy. In general it takes between 6 to 8 hours for the body to burn through its glycogen supply. When glycogen is depleted the body will then turn to the energy stored in fat cells.

Eating throughout the day, or even the basic three square meals a day format, makes it much harder for the body to burn fat. Extending the time between eating will force your body to tap into the fat reserves. Guess what that means? Get ready to synch up your belt and go shopping for smaller clothes!

The Cautions – Is Intermittent Fasting For Everyone?

Because one of the major effects of fasting is to reduce blood sugar, those dealing with low blood sugar (hypoglycemia) would be wise not to implement a fasting routine until your glucose and insulin levels are well managed. Working on your overall diet, limiting sugary foods and grains while increase fat and protein, should probably come first.

There are actually several studies that show fasting while pregnant can be beneficial.3,4,5 However these were all done on healthy women and did show evidence that there is less room for error in providing proper nutrition for the women and her baby. It is probably safer to avoid it. Besides only pregnant and nursing women, females in general may want to carefully evaluate their overall health before adopting a fasting routine.

While healthy women should certainly consider the many benefits fasting offers, they should be aware that fasting can become a source of stress if one becomes fixated on hunger pangs or watching the clock tick away until it’s time to eat again. As in all prolonged stressful situations, cortisol rises and adrenal glands can become overworked. The result can be fatigue, anxiety, and irregular periods due to the hormone disruption.

The effects of stress on hormones happen faster in women. Fasting sends a stress signal of “famine” to the body. For men, reproducing during famine would be a slight inconvenience. For women, the risks of reproducing during famine are much more severe, thus the more dramatic physical/hormonal response.

That said, both men and women who are already chronically stressed or dealing with irregular cortisol levels should carefully consider their health and all their options before fasting.

The How’s – What’s the Best Way to Get the Benefits of Intermittent Fasting?

Intermittent fasting is best approached as a shift in lifestyle and eating patterns, not a diet. There’s no need to count calories or measure grams. Simply focus on the healthy foods you already eat with a particular emphasis on healthy fats and proteins.

While there are many fasting schedules you can adopt, like mentioned at the very beginning of this article, what I’ve found to be the easiest practice for me and many others is simply skipping breakfast. Assuming you ate dinner at 6pm, then didn’t eat again until lunch the next day at 12pm, you’ve fasted for 18 hours, well beyond the 6 to 8 hours required to burn through glycogen stores and start burning fat. You’ll get plenty of benefits by taking it slow at first, like dinner at 7pm and your first bites at 11am for example.

If you exercise while fasting, don’t attempt to continue your fast after your workout. That puts a type of stress on your body and brain that you don’t want. If you work out in the morning, eat a high quality protein-heavy meal soon afterwards then simply skip lunch and don’t eat again until dinner.

Keep in mind that it is the consumption of protein and carbohydrates that will tell the body to stop burning fat. A cup of black coffee or unsweetened green tea in the morning, even with a spoonful of pure fat like coconut oil, can be beneficial in helping you feel satisfied until lunch time.

Be aware that it may take a few weeks to a few months for your body to get the message that you’re serious about making it burn fat. Once it clearly gets the idea it will begin increasing its production of fat burning enzymes and turn into a fat burning furnace.

As always, pay attention to your body and make careful evaluation of your own situation and needs. If you’re already healthy and eating well, intermittent fasting can be just the thing you need to break out of a plateau and take your health and performance to the next level.


Jaeger PA, Wyss-Coray T. All-you-can-eat: autophagy in neurodegeneration and neuroprotection. Mol Neurodegener 2009; 4:16

Intermountain Medical Center, Eurekalert April 3, 2011

J Obstet Gynaecol Res. 2007 Apr;33(2):151-4. Effect of maternal fasting on uterine arterial blood flow.

J Obstet Gynaecol Res. 2008 Aug;34(4):494-8. doi: 10.1111/j.1447-0756.2008.00814.x. Effect of fasting during Ramadan on fetal development and maternal health.

Arch Gynecol Obstet. 2009 Feb;279(2):119-23. doi: 10.1007/s00404-008-0680-x. Epub 2008 May 17. The effect of Ramadan fasting on maternal serum lipids, cortisol levels and fetal development.

by Brad Shepherd @DrAxe