Is fasting safe?  It’s not that easy.

Is fasting safe? It’s not that easy.

Today, many people are using some form of fasting to manage and promote health, but there is ongoing confusion around the aspect of timing.  How long is too long?  How often is too often?  When should you start and stop eating each day?  Emerging research is helping to answer these questions.

First, let’s define the different methods of fasting:

Intermittent fasting (IF) regimens usually encompass a period in which only water is consumed or calorie intake is very low, which is followed by a normal feeding period that in most cases lasts between 12 and 48 hours. IF includes various eating patterns repeated daily to once per week and may include:

  • Severely restricted (over 50%) calorie intake lasts between 12 and 48 hours
  • Alternate day fasting which consists of complete water-only fasting that occurs every other day.
  • 70% energy restriction every other day
  • the 5:2 diet, which provides between 500 and 700 calories for 2 days per week.
  • time-restricted feeding (TRF), in which food intake is in most cases restricted to 6–12 hours per day.

Prolonged fasting (PF) refers to a prolonged and severely calorie-restricted (like Prolon fasting mimicking diet) or water-only fasting period lasting in most cases between 48 hours and 1 week. This is usually done a limited number of times each year ranging from monthly to quarterly or as needed to treat a medical condition. 

Per Dr. Valter Longo, PhD, daily fasting has not been shown to be safe, in fact it may be damaging to our health due to increased stress on the body.  This means that restricting your eating window each day (often skipping breakfast) may help you drop weight, but may not be the anti-aging trick we once thought it was.  That said, his research shows that intermittent and periodic fasting (IF and PF) are very safe and effective strategies for cellular aging and reducing age-related disease if done in moderation.

His 2021 study concluded that IF lasting from 12 to 48 hours and repeated every other day to every 7 days as well as PF lasting 2 to 7 days and repeated once per month or less have the potential to promote longevity and reverse chronic diseases associated with lifestyle, diet and aging.

IF and PF in this cadence are also being studied for cancer, autoimmunity, neurodegeneration and metabolic and cardiovascular disease.

You’ll note that his expert team suggests NOT restricting your daily feeding-window to less than 12-hours on a daily basis.  This means if you eat your first meal at 7am and finish by 7 pm, in your normal routine, you’re supporting good health and that restricting windows or calories is best done in cycles that including re-feeding between those periods of fasting.

Consider that your cortisol levels are highest in the morning and while we think about cortisol as a “stress hormone”, it is really an activation hormone.  In the morning, we are primed to wake up and get going, in large part due to a higher level of cortisol.  However, if you drink coffee (stimulant) and skip breakfast (stressor), you may not be supporting energy and productivity.  In fact, you may be relying too heavily on your stress response to keep you going instead of on fuel (food).  

This may be why another group of researchers found that while restricting the window of eating to 4 to 6-hour did lead to weight loss, it also reduced DHEA levels in women.  This reduction can lead to reduced immune function, reduced resilience and reduced testosterone levels. 

So is fasting safe? 

The research points towards cyclical fasting as a healthy method to boost health and longevity.   Daily time-restricted-eating or daily intermittent fasting can lead to malnutrition and elevated stress on the body if practiced long-term without periods of re-feeding. 

To keep energy stable, blood sugar balanced and nutrient storage high, our team suggests starting your day with a high fiber and low-carb breakfast, and closing your eating window 3 hours before bed.  This eating pattern mirrors our circadian rhythm and fuels proper energy and resting cycles throughout the day.

Fasting with Prolon once every 30-120 days or cycling intermittent fasting (caloric restriction) 1-2 days per week are tools to support healthy aging and disease prevention when used appropriately for your lifestyle and health goals.  Talk to our team if you want a plan designed for your needs.