Intermittent fasting has been steadily gaining popularity, but what does the scientific research say about the benefits of intermittent fasting on health and disease?
Modern conveniences and lifestyle have drastically changed not only what we eat, but how and when we eat. These changes have occurred over time, but they may not all be healthy. In a typical western diet, most people will consume three meals per day – perhaps with a few snacks in between. As a society, we have become increasingly sedentary, and un-scheduled physical activity is not typically part of our natural routine. These dietary and lifestyle changes have significant impacts on health and well-being. Reviewing the research on intermittent fasting provides evidence to support that this lifestyle change could help to improve overall health, as well as the development of chronic disease.
Intermittent fasting is characterized as alternating periods of eating and fasting. A typical intermittent fast might consist of a period of 16 hours of fasting – during which water, coffee, or tea may be freely consumed – followed by an eight-hour non-fasting period. During this time there are typically no restrictions on what kinds of foods you are able to eat. Other forms of intermittent fasting can include alternate day fasting, or fasting for two days per week.
According to the science, intermittent fasting may be beneficial for health and well-being, in addition, this lifestyle may be useful in preventing or fighting disease. Studies in mice and rats have uncovered potential benefits of intermittent fasting for a variety of conditions, including heart disease, Alzheimer’s and Parkinson’s disease, cancer, diabetes, and stroke. Below is an intermittent fasting review, covering some of the research that is revealing the potential of intermittent fasting to impact human health and disease.
Weight loss
Intermittent fasting has certainly gained significant attention as a way to lose weight. In fact, clinical trials have found that intermittent fasting is effective for weight loss – in some cases as effective as a calorie-restricted diet. Further beneficial effects have been noted, including reduced triglycerides and reduced cholesterol.
There is some evidence to suggest that people are more likely to stick to an intermittent fasting diet. This might be because on the non-fasting days there is little restriction on what can be eaten. This is different from a regular calorie-restricted diet, which might be difficult to stick with since the amount and types of food are typically restricted with these diets. This makes them a difficult long-term commitment, ultimately resulting in non-compliance.
Typical side effects that have been associated with intermittent fasting include headache and light-headedness, as well as constipation in some cases.
Type 2 diabetes
Participants on intermittent fasting programs have not only reported weight loss but reductions in fasting insulin and insulin resistance. In some cases, these reductions have been greater than reported for calorie-restricted diets.
Although more research is needed to further investigate the benefits of intermittent fasting for diabetes, the results to date suggest that this program could reduce the risk of type 2 diabetes in people who are overweight or obese, and could help to improve insulin resistance in diabetes patients.
Cardiovascular disease
According to the results of clinical trials, in patients who are overweight or obese, intermittent fasting can improve blood glucose and insulin levels, as well as reduce resting heart rate. A clinical trial that included patients who were on a two-month program of alternate-day fasting found that total cholesterol, LDL cholesterol, and triglycerides were reduced in these patients. In one study, the reductions in cholesterol were greater than the reductions that were seen for participants who were on a calorie-restricted diet. Similar reductions in blood pressure have been reported for both calorie-restricted diets and intermittent fasting.
Rheumatoid arthritis
A clinical trial that included patients who were previously diagnosed with rheumatoid arthritis compared patients who were participating in Ramadan with a group of patients who were not fasting. The study reported significant improvements in disease activity scores in both men and women who were in the fasting group. However, as stated by the researchers, there was no way in this study to determine whether these positive changes were a result of changes to macronutrient consumption during the fasting month or a result of the fasting itself. Further study will be necessary to confirm and expand upon these findings.
In another study that included patients fasting during Ramadan, researchers assessed disease activity in fasting patients six months prior to the initiation of fasting, and at a second time-point at least seven days after the fasting period. The researchers reported reduced disease activity scores in these patients, providing further evidence that intermittent fasting may help to reduce disease activity.
Additional benefits of intermittent fasting
Although there is a lack of data from clinical trials that provide evidence of direct benefit, there is indirect evidence to suggest that intermittent fasting may be beneficial for neurodegenerative diseases such as Alzheimer’s and Parkinson’s, stroke, cancer, and multiple sclerosis.
In general, it is thought that intermittent fasting may be beneficial in the prevention of diseases for which obesity and aging are risk factors.
Side effects of intermittent fasting
Typical side-effects associated with intermittent fasting include fatigue, nausea, and headache. Fasting is not recommended for women who are pregnant or breastfeeding, children, or people who are underweight. Even if you don’t fall into one of these categories, you should always speak to your doctor if you intend to begin a fasting regimen to make sure this is a safe option for you.
References:
Mattson, M. P., Longo, V. D., & Harvie, M. (2017). Impact of intermittent fasting on health and disease processes. Ageing research reviews, 39, 46–58. https://doi.org/10.1016/j.arr.2016.10.005
Ben Nessib, D., Maatallah, K., Ferjani, H. et al. Impact of Ramadan diurnal intermittent fasting on rheumatic diseases. Clin Rheumatol 39, 2433–2440 (2020). https://doi.org/10.1007/s10067-020-05007-5
Siddique, S., Imran, Y., Afzal, M. N., & Malik, U. (2020). Effect of Ramadan fasting on disease activity in patients with rheumatoid arthritis presenting in tertiary care hospital. Pakistan journal of medical sciences, 36(5), 1032–1035. https://doi.org/10.12669/pjms.36.5.2099
Phillips M. (2019). Fasting as a Therapy in Neurological Disease. Nutrients, 11(10), 2501. https://doi.org/10.3390/nu11102501
Mattson, M. P., Longo, V. D., & Harvie, M. (2017). Impact of intermittent fasting on health and disease processes. Ageing research reviews, 39, 46–58. https://doi.org/10.1016/j.arr.2016.10.005
Ganesan K, Habboush Y, Sultan S. Intermittent Fasting: The Choice for a Healthier Lifestyle. Cureus. 2018;10(7):e2947. Published 2018 Jul 9. doi:10.7759/cureus.2947
Rynders CA, Thomas EA, Zaman A, Pan Z, Catenacci VA, Melanson EL. Effectiveness of Intermittent Fasting and Time-Restricted Feeding Compared to Continuous Energy Restriction for Weight Loss. Nutrients. 2019;11(10):2442. Published 2019 Oct 14. doi:10.3390/nu11102442
Mattson, M. P., Longo, V. D., & Harvie, M. (2017). Impact of intermittent fasting on health and disease processes. Ageing research reviews, 39, 46–58. https://doi.org/10.1016/j.arr.2016.10.005
Barnosky AR, Hoddy KK, Unterman TG, Varady KA. Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: a review of human findings. Transl Res. 2014;164(4):302-311. doi:10.1016/j.trsl.2014.05.013
