Intermittent fasting (often referred to as simply IF) is an eating pattern that cycles between periods of fasting and periods of eating[1]. It does not dictate what a person should eat, but instead when a person should eat. Multiple intermittent fasting methods exist including the most common of fasting for 16 hours each day while eating during 8 hours, or the less common method of fasting for 24-hours once or twice per week. Intermittent fasting is generally safe and has proven as effective in weight loss as any other diet or positive nutritional change. Many other health benefits to intermittent fasting have been confirmed in studies on mice, and are hypothesized and currently being studied in humans.

Humans have evolved to function in cycles based on an internal clock known as the circadian rhythm. Each individual’s circadian rhythm may be slightly different, but for the most part our metabolism cycles to sleep at night and eat during the day. Nighttime eating is well established to be associated with a higher risk of obesity and diabetes. Circadian rhythm fasting is intermittent fasting where a person eats within the early 8-10 hours of the day and then fasts throughout the remaining hours of the evening and night. There is some evidence to suggest there are weight loss benefits to this type of intermittent fasting, when combined with a healthy diet and lifestyle.

When circadian rhythm fasting isn’t considered, and intermittent fasting is studied in that fasting takes place in the morning or day, while eating is allowed during evening hours, the results show that it is as beneficial as any other diet. This is likely a simple result of less opportunity to over-eat when time constraints are in place. A client that is prone to habitually over-eating or who has intense cravings in the evening, may be well suited to intermittent fasting where they fast in the morning and eat during the later 8 hours of their day to help curb the amount of food they can consume.

Intermittent fasting can be extremely difficult for some people, and those with certain medical conditions like advanced diabetes, or a history of eating disorders like anorexia or bulimia, or those who are pregnant or breastfeeding should not attempt intermittent fasting without first consulting their primary physician[2].  A well-balanced, nutrient-dense, consistent diet that is rich in real foods, and that is most sustainable is always the best option.

[1] https://www.healthline.com/nutrition/intermittent-fasting-guide#what-it-is

[2] https://www.health.harvard.edu/blog/intermittent-fasting-surprising-update-2018062914156