Is Intermittent Fasting Good For Us? A Systematic Review
Title: Health effects of intermittent fasting: hormesis or harm? A systematic review
Author: Horne et al
Journal: American Journal of Clinical Nutrition
Objective: “To identify rigorous, clinically relevant research studies that provide high-quality evidence that therapeutic fasting regimens are clinically beneficial to humans.”
Previously, I have reported on many of the potential benefits of intermittent fasting. This includes:
In animal models, we see the following potential benefits:
- Extend lifespan, improve health
- better insulin control, reduced nerve cell injury
- reduced risk of diabetes, heart disease, certain types of cancer
- Improved immune system
In various human studies, we see the following potential benefits
- asthma, inflammatory markers
- reduce heart rate, blood pressure, cholesterol, triglyceride
- alzheimers, parkinsons
- reduce inflammatory markers
- risk of diabetes (in at risk folks)
- increase human growth hormone
Unfortunately, these are mostly done in either animal models or very, very limited human studies and the ability to draw definitive conclusions is very limited.
The authors of this study sought to evaluate the clinical evidence that intermittent fasting is beneficial on clinically relevant outcomes such as weight, cholesterol, diabetes, coronary heart disease, etc.
The authors used a systematic review by looking at research published on intermittent fasting from various research databases.
A systematic review, similar to a meta-analysis, seeks to combine and summarize the results different studies on a given subject in the hope of identifying patterns among study results. It is the gold standard among scientists and medical professionals for interpreting research results.
The authors were only able to identify 3 randomized clinical trials (yes only 3!) of fasting in humans with a total of 5 published articles. Between these studies, the authors found that intermittent fasting had positive results regarding surrogate outcomes such as:
- Reduction in body fat
- Lower triglycerides, LDL cholesterol and C-reactive protein
There were two observational studies that found fasting was associated with a lower prevalence
- coronary artery disease (CAD)
The data and research for intermittent fasting is very limited. Most studies thus far are small and limited in scope and outcome and there are virtually no large-scale, well designed studies.
The few randomized clinical trials and observational studies do suggest potential health benefits, however, much more research is needed.
Until there is better evidence, the ability of healthcare professionals to recommend fasting as a health intervention will be limited.
Horne, B. D., Muhlestein, J. B., & Anderson, J. L. (2015). Health effects of intermittent fasting: hormesis or harm? A systematic review. American Journal of Clinical Nutrition, 102(2), 464-470. doi:10.3945/ajcn.115.109553