Dr. Steven Scappaticci, B.Sc. (Hons.), CSCS, DC, FRCms
If you’re unfamiliar with ‘Intermittent Fasting’, there’s no clear definition but simply put it’s a term for cycling your diet between periods of fasting and non-fasting. The key is that this is all occurring withoutmalnutrition. This may sound similar to how you normally eat; however you’ll see how it may differ from what you do on a daily basis.
As with many aspects of nutrition, there are many debates, myths, and controversies. Intermittent fasting is not immune to these! But for the purpose of this article, we’ll just focus on the basic overview of intermittent fasting.
With intermittent fasting there is a designated period where you can eat and the rest of the time in the day is reserved for fasting. Within a 24-hour period, you are in one phase or the other; you do not continuously go back-and-forth between the two. There are many forms of intermittent fasting.
A common form is fasting for 15-16 hours straight and then allowing yourself an 8-9 hour window to eat all the days’ meals. This is a nice amount of time to get you in a true fasted state however, short enough to avoid putting your body into the proposed “starvation mode”. If this sounds difficult, a common tip is using your sleeping hours (i.e. 8 hours) to contribute to this fasting window.
This may not be where a beginner would start though; perhaps a smaller fasting window is the place to start. For some, they will take it further by altering their “windows” to allow for greater time in the fasted state (e,g, Warrior Diet – 20 hour fast, 4 hour fed). Some fast every day, some do ‘alternate day modified fasts’ and some even do the occasional ‘whole day fast’, there are many variations. Remember, its fasting WITHOUT malnutrition!
You may be asking yourself, ‘why would anyone want to fast?’ Believe it or not there are a number of reasons. Decades ago fasting was used as a primary treatment option for obesity, however today you may find people fasting for religious reasons, non-obesity related fat loss, a hunger strike, and famine just to name a few .
When one stops eating the body will begin to digest the contents found within the digestive tract followed by the remaining glycogen stores in the liver . If you were to venture on that 16-hour fasting journey, the fasted state truly doesn’t begin until around hour 12! In the fasted state, insulin levels are low since the glucose in the body has been utilized as fuel already and the body then switches to utilizing fat as its fuel .
This is the major proponent of intermittent fasting; the body spends enough time fasting to truly get to a state where fat is utilized. Given the typical North American lifestyle, one could see how people have trouble getting to this phase.
The benefits of intermittent fasting have been noted, but at the same time are still considered to be in the preliminary research phase. There appear to be many cardiovascular benefits such as: increased HDL (the good cholesterol), decreased LDL & triacylglycerol, and improvements in blood pressure, just to name a few. Similarly, it can improve insulin concentrations & sensitivity, which is important for controlling diabetes risk .
It should be noted, many of the immediate benefits, specifically weight loss, have been seen in both intermittent fasting as well as the more traditional methods of calorie restriction . This is simply due to both of these methods having the ability to put an individual in a caloric deficit, allowing them to lose weight. But does intermittent fasting provide some benefit that regular caloric restriction doesn’t?
With regards to the long-term beneficial effects of fasting, it seems to be difficult to conclude due to the lack of long-term human studies. On the one hand, The National Institute on Aging released, just last fall, a report highlighting that mice who increased their time between meals were healthier and lived longer than mice who ate more frequently . But let’s not jump to conclusions as this happened in mice, not humans; but the results are still interesting nonetheless.
Given the hypotheses surrounding the mechanisms of intermittent fasting, one may think that the reduction in free radical production that comes with food restriction may result in less cellular oxidative damage. Oxidative stress comes on through many processes and eating is one of them. Some argue that the reduced oxidative damage may prevent telomere shortening and that’s the effect fasting has on aging. Does this have a link to longevity? Maybe but it may be too soon to conclude in humans .
One last interesting piece regarding intermittent fasting and ones longevity is the beneficial effects of autophagy. Autophagy is a process our body uses to breakdown and recycle damaged cells. It is a protective mechanism in many areas of the body with some studies claiming that abrogation of autophagy, specifically in neurons can lead to disease . Although we know the body will resort to “eating itself” in the fasted state, there is still research needed to strengthen the ties between autophagy and the protective effects against certain systemic diseases.
Intermittent fasting is not for everyone, as there are relative contraindications. If you have a poor diet, poor sleep habits, excessive stress, issues with fasting and your training times, or hormonal issues/other medical conditions (e.g. cancer), intermittent fasting may not be for you at the moment . Please contact a regulated health professional with regards to if intermittent fasting is right for you!
This article is solely meant to be “food for thought” and in no way attempts to skew you to one side or the other. If you’re familiar with intermittent fasting hopefully you’ll find this article to be a good overview. If this is a new concept, I encourage you to delve further if you’re interested. For any other questions or comments, feel free to contact me directly!
 Davis, C S; Clarke, R E; Coulter, S N; Rounsefell, K N; Walker, R E; Rauch, C E; Huggins, C E; Ryan, L (25 November 2015). "Intermittent energy restriction and weight loss: a systematic review". European Journal of Clinical Nutrition. 70(3): 292–299. doi:10.1038/ejcn.2015.195
 Johnstone, A. (2015). Fasting for weight loss: an effective strategy or latest dieting trend? International Journal of Obesity. 39, 727-733.
 Intermittent Fasting (Time-Restricted Eating)
 Rose, Chip. (06 September, 2018). Longer daily fasting times improve health and longevity in mice. National Institute on Aging – U.S. Department of Health & Human Services.
 Himbert, Caroline, Thompson, Henry, Ulrich, Cornelia M. (2018). Effects of Intentional Weight Loss on Markers of Oxidative Stress , DNA Repair and Telomere Length –a Systematic Review. The European Journal of Obesity. 10(6): 648-665.
 Alirezaei, Mehrdad, Kemball, Christopher C., Flynn, Claudia T., Wood, Malcolm R., Whitton, J. Lindsay, Kiosses, William B. (2010). Short-term fasting induces profound neuronal autophagy. Autophagy. 6(6): 702-710.