By: Dr. John Bagnulo, Director of Nutrition

One of the most medicinal nutrition practices is the practice of not eating, at least for a limited or moderate amount of time. Over the course of human evolution this has served our species well, at least as well as it serves other mammals and as has been observed in numerous animal studies. Fasting provides the body with a window for unique immune function, an ability to discard the metabolic clutter that is hindering cellular function, and ways to recycle those aspects of our metabolic hardware that need to be replaced. These processes require a shortage of calories, carbohydrates, and/or protein to be switched into the "on" position and if we are constantly in a "fed" state we miss out on one of the true physiological feats of evolution.

Made more popular recently by several different types of highly publicized limited-fasting plans, there isn’t a one-size-fits-all duration or frequency of fasting. There are various approaches that utilize self-imposed caloric or macronutrient restriction that have proven effective for countless individuals who previously failed with the general "less of everything in moderation" approach. Research is very supportive of its overall benefits, so long as it is not carried out too far and not attempted during specific phases of the life cycle (not a great idea for young children or pregnant women, obviously). It is more reflective of the ancestral or Paleo lifestyle where we were not always surrounded by food, never mind toxic food, and had more significant windows of time where our bodies needed to alter their biochemistry to conserve, recycle, and shift metabolically.

Being metabolically flexible is probably the greatest benefit of fasting overall. If our body can only use carbohydrates as a fuel and never needs to switch over to ketones or fats as the primary energy sources, we can create a storm on the endocrine, cardiovascular, and neurological fronts. Fasting is an approach that should be considered as a viable tool to improve mental clarity, beat a difficult infection, or reverse insulin resistance. Increasing the window of time without eating significant amounts of protein or carbohydrate can be a very healthy and effective means of supporting our innate, metabolic, detox efforts.

Autophagy is the best example of this. The ability of a cell to initiate its own digestion of defective mitochondria and other cellular organelles is in some ways, the only way we can eradicate some types of infections. The herpes virus for instance, carried by over half of humans and responsible for everything from cold sores to serious neurological complications, has the unique ability to hide in our cells and keep normal defense systems turned off. So much ahead of our own evolution, this virus is often undetected. Even when it is detected it cannot be eradicated with normal immune-triggered autophagy or apoptosis. In cases like this, and there are numerous other ones, only an extended window of fasting (typically 16+ hours) provides the environmental stimuli for this internal "house cleaning." Eliminating damaged and underperforming mitochondria, recognizing mutated DNA, and initiating the destruction of infected cells are important processes required to stay healthy and to age well.

Fat is the most forgiving source of energy when it comes to enabling "fasting" benefits even in the absence of a true fast. The source of that fast is critical though. Staying with predominantly saturated fats like those found in extra virgin coconut oil, grass-fed butter, and macadamia nuts, or monounsaturated fats like those in extra virgin olive oil and avocados, will be much more effective and healthier overall. Limiting protein is the most important restriction for enhanced autophagy, followed closely by available carbohydrates. Available or net carbohydrate does not count the fiber that is found in many higher fiber foods. This makes the coconut a great example of a "fasting-friendly" staple. Rich in saturated fat, with very little protein or available sugar, the coconut is one of the best foods to have in the morning on days that you would like to eat something but want to try the practice of intermittent fasting for whatever reason.


Wegman MP et al. Practicality of intermittent fasting in humans and its effect on oxidative stress and genes related to aging and metabolism. Rejuvenation Res. 2015 Apr;18(2):162-72.

Tinsley GM and LaBounty PM. Effects of intermittent fasting on body composition and clinical health markers in humans. Nutr Rev. 2015 Oct;73(10):661-74.

Dr. John Bagnulo is the Director of Nutrition at Functional Formularies and leads nutrition research and development initiatives. Learn more about Dr. Bagnulo here.