Intermittent fasting is a dietary pattern of periods of fasting and feeding that occur on a schedule.  There are different types such as alternate day fasting (ADF), which is 24 hours of eating normally followed by 24 hours of fasting, and time-restricted feeding (TRF).  During TRF a person ingests a full day’s worth of calories in a specific time span and then fasts the remainder of the day.

The literature regarding IF supports several metabolic health benefits which include: weight loss, reduced insulin resistance, decreased blood glucose levels, reduced blood pressure, and improved lipid profile.  In addition, IF contributes to cardiac protection, diabetes prevention, cancer prevention, protection against neurodegeneration, and reduction of inflammation.  As a result of these changes, the prolongation of an individual’s lifespan ensues.

IF has shown promising results for weight loss and reduction of BMI.  Individuals with high BMIs are at risk for metabolic syndrome.  Metabolic syndrome is a condition characterized by obesity, insulin resistance, hyperglycemia, hypertension, hypertriglyceridemia, and low high-density lipoprotein cholesterol (HDLc).  It increases the risk of cardiovascular disease, diabetes type II, coronary heart disease, stroke, vascular dysfunction, and many other disorders.  By reducing a person’s weight, which is a by-product of IF, several metabolic changes occur.  IF lowers leptin levels, which improves insulin sensitivity and overall glucose levels.  Furthermore, reduction of an individual’s weight contributes to lower blood pressure and better cardiovascular health due to lower cholesterol and triglyceride levels.  Also, IF induces the release of hypoadiponectin which protects the heart against ischemic injury.

Another helpful byproduct of IF is that it decreases the expression of proinflammatory cytokines thereby reducing body inflammation.  This goes hand in hand with another benefit of IF which is neurodegeneration protection.  Fasting stimulates the production of brain-derived neurotrophic factor (BDNF) which aids in cognitive function, among other things.  Through reduced inflammation pathways and the stimulation of BDNF, neurons are better protected against tissue injury.  There is also evidence towards nerve cell restoration and synapse formation. 

As with any diet, individuals are encouraged to seek medical advice before initiating.  While IF has many benefits, it is not recommended for all populations such as those who are pregnant or those with uncontrolled diabetes, chronic kidney disease, or other chronic health conditions.  Fasters may also endure side-effects of this lifestyle upon initiation.  Some of these side-effects include: dehydration, headache, heartburn, constipation, anemia, and poor sleep.  While these typically don’t cause any significant suffering, it is important to seek medical attention if they do not subside.

IF isn’t the easiest diet to follow.  Some find it difficult to stick with due to psychosocial influcences.  Fasters have said it is sometimes difficult to maintain fasting when one is expected to attend business lunches, dinners, or parties for work or personal reasons.  Also, this diet has high non-compliance rates due to unhappiness with the restrictions and excessive hungriness. Many overeat and exceed calorie intake requirements when breaking the fast due to excessive hunger.  Therefore, the sustainability of IF is questionable despite the proposed health benefits.