Fasting is a practice that has been around for thousands of years, but over the past decade, it has become quite the hot topic in the media for weight loss and overall health. 

So what exactly does Intermittent Fasting entail? The answer is, it depends who you ask… Here are the main categories of fasting that are practiced (graph taken from Academy of Nutrition and Dietetics):

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Ok great! So we know what intermittent fasting can include, so the big question is…
Does it work??
As a disclaimer: The studies done on intermittent fasting are extremely limited and the majority of them are done on animals… not humans. Many of the studies also do not take into other lifestyle changes such as exercise, quality of food, stress levels, etc. This means that these studies give us a lead, but more information is needed before we can have concrete recommendations.

What studies are telling us:

  • All forms of fasting resulted in some (not always a lot) weight loss in the studies
  • There were a few positive changes in lipid markers, but they were insignificant, and the studies were based off very small groups
  • Nighttime fasting (not eating during the night) significantly helped improved metabolic markers, reduced risk of obesity, and reduce obesity related conditions (non-alcoholic fatty liver disease, diabetes, heart disease) IN ANIMALS– limited data for humans
  • Fasting periodically does not seem to have a negative impact mood overall- but did show fluctuations in mood during the actual intense hunger stages
  • There is some evidence that routine fasting methods could help with gut health
  • There is no evidence that doing an alternate day fasting regimen is any better than reducing calories overall​
Essentially, the studies so far offer positive potential for intermittent fasting, but we are far from having enough evidence to recommend fasting for everyone. If someone is looking for weight loss, and fasting is motivating for that individual, some variations of intermittent fasting might be effective. 

​Cons of intermittent fasting:

  • Can become dangerous if the individual starts missing key nutrients frequently.
  • Can negatively affect certain individual’s relationship with food and lead to disordered eating
  • If you get ‘hangry’, fasting can lead to some emotional stress 
Key Points for Intermittent Fasting:

  • Intermittent Fasting can be done in several ways:
    • Alternate Day Fasting- Alternate days of eating 0 calories, and days  of normal eating patterns (number of days fasted in a month ranges on the person)
    • Modified Fasting (5:2 fasting)- 2 days of restricted calories (20-25% of calorie needs) and 5 days of normal eating during the week
    • Time restricted fasting- Fasting based off the time of day. This could mean avoiding night eating, only eating in the afternoon, only eating in the morning, etc.
    • Religious Fasting- Fasting regimens done for religious practices (examples- Ramadan for Islamic religions, extended nighttime fasting for Seventh Day Adventists, routine fasting days for members of the Church of Jesus Christ, etc.
  • Avoiding food at night could potentially help with your sleep and reduce risk for chronic diseases
    • **Note that going to sleep hungry can effect your sleep pattern, so try to focus on a healthy full dinner and avoid snacking in the late evening/ middle of the night. 
  • Certain methods of fasting could help with weight loss & reducing inflammation
  • Intermittent fasting does not follow our intuitive feeding cues
  • Intermittent Fasting is NOT for everyone. It may affect someone’s relationship with food and result in unneeded stress or disordered eating.
  • Main Take Away: Every mind and body is different. Always work with a dietitian if you are going to start a fasting regimen. They can look at your individual situation and see if it would be safe and if it would be effective.
References:

  • Catterson, J., Khericha, M., Dyson, M., Vincent, A., Callard, R., Haveron, S., . . . Partridge, L. (2018). Short-Term, Intermittent Fasting Induces Long-Lasting Gut Health and TOR-Independent Lifespan Extension. Current Biology, 28(11), 1714-1724.e4.
  • Frey, Rebecca. “Intermittent Fasting.” (2019): 746-51. Web.​
  • Patterson, R., Laughlin, G., LaCroix, A., Hartman, S., Natarajan, L., & Senger, C. et al. (2015). Intermittent Fasting and Human Metabolic Health. Journal Of The Academy Of Nutrition And Dietetics115(8), 1203-1212. doi: 10.1016/j.jand.2015.02.018