Intermittent fasting is an umbrella term for a mixture of diets that cycle between a period of fasting and non-fasting. With this kind of fasting, normal amounts of food are eaten in a smaller time frame. Thus, intermittent fasting is not a diet, but a pattern of eating that reduces the window of eating each day to around eight hours.

There are several types of intermittent fasting and two variations are mentioned below:

• Alternate day fasting (ADF): ADF involves a 24-hour fasting period, followed by a 24-hour non-fasting period. Studies have suggested that ‘alternate day fasting’ may prolong one’s life span. One study had their subjects consume food on alternate days, either 900 calories or 2300 calories (averaging 1600 calories) and the body weight was maintained. This means the participants consumed either 56% or 144% of their daily caloric requirement.
• Modified fasting: This involves restricting caloric intake to about 20% of normal intake on fasting days, instead of intense calorie restriction.

Some studies have been conducted that reveal potential benefits of intermittent fasting. 

Studies have suggested that fasting can limit inflammation. Short-term inflammation is a positive thing and is the normal first line of defense in the body to fight-off foreign agents. Long-term inflammation can cause various diseases like heart disease, cancer, metabolic syndrome, Alzheimer’s disease, and various other degenerative conditions. A study, published in the Iranian Journal of Basic Medical Sciences, suggested that Ramadan fasting, a period of fasting for 29-30 days, is fairly safe for normal, healthy adults. The study also revealed that it might be very useful in decreasing the cholesterol and triglyceride levels in individuals who have abnormal amounts of lipids in their blood.

Intermittent fasting can also help individuals with high blood sugar levels. A study from the Gerontology Research Center suggested that intermittent fasting has helpful effects on blood sugar regulation and brain cell resistance to injury in mice. Another study from the University of Kentucky revealed that food restriction for 2-4 months in mice could resist brain cell loss in the region of the brain responsible for learning and memory, called the hippocampus. In fact, the resistance to brain cell loss increased when the mice underwent food restriction. Individuals, who underwent intermittent fasting or caloric restriction also found a reduction in blood pressure.

Even though intermittent fasting is beneficial to one’s health and body in many ways, it may not be suitable for everyone. It is always advisable to talk to the healthcare provider to assess a fasting diet’s suitability. It is recommended that individuals with a history of eating disorders should not try this pattern of eating.

Additional Resources:

Anson, R. M., Guo, Z., de Cabo, R., Iyun, T., Rios, M., Hagepanos, A., ... & Mattson, M. P. (2003). Intermittent fasting dissociates beneficial effects of dietary restriction on glucose metabolism and neuronal resistance to injury from calorie intake. Proceedings of the National Academy of Sciences, 100(10), 6216-6220.

Antoni, R., Johnston, K. L., Collins, A. L., & Robertson, M. D. (2014). The Effects of Intermittent Energy Restriction on Indices of Cardiometabolic Health.

Brown, J. E., Mosley, M., & Aldred, S. (2013). Intermittent fasting: a dietary intervention for prevention of diabetes and cardiovascular disease?. The British Journal of Diabetes & Vascular Disease, 13(2), 68-72.

Bruce‐Keller, A. J., Umberger, G., McFall, R., & Mattson, M. P. (1999). Food restriction reduces brain damage and improves behavioral outcome following excitotoxic and metabolic insults. Annals of neurology, 45(1), 8-15.

Duan, W., & Mattson, M. P. (1999). Dietary restriction and 2‐deoxyglucose administration improve behavioral outcome and reduce degeneration of dopaminergic neurons in models of Parkinson's disease. Journal of neuroscience research, 57(2), 195-206.

Mager, D. E., Wan, R., Brown, M., Cheng, A., Wareski, P., Abernethy, D. R., & Mattson, M. P. (2006). Caloric restriction and intermittent fasting alter spectral measures of heart rate and blood pressure variability in rats. The FASEB Journal, 20(6), 631-637.

Mohajeri, F. A., Ahmadi, Z., Hassanshahi, G., Mohajeri, E. A., Ravari, A., & Ghalebi, S. R. (2013). Dose Ramadan Fasting Affects Inflammatory Responses: Evidences for Modulatory Roles of This Unique Nutritional Status via Chemokine Network. Iranian journal of basic medical sciences, 16(12), 1217.

Stote, K. S., Baer, D. J., Spears, K., Paul, D. R., Harris, G. K., Rumpler, W. V., ... & Mattson, M. P. (2007). A controlled trial of reduced meal frequency without caloric restriction in healthy, normal-weight, middle-aged adults. The American journal of clinical nutrition, 85(4), 981-988.

Yu, Z. F., & Mattson, M. P. (1999). Dietary restriction and 2‐deoxyglucose administration reduce focal ischemic brain damage and improve behavioral outcome: Evidence for a preconditioning mechanism. Journal of neuroscience research, 57(6), 830-839.

Helpful Peer-Reviewed Medical Articles:

Danaei, G., Finucane, M. M., Lu, Y., Singh, G. M., Cowan, M. J., Paciorek, C. J., ... & Rao, M. (2011). National, regional, and global trends in fasting plasma glucose and diabetes prevalence since 1980: systematic analysis of health examination surveys and epidemiological studies with 370 country-years and 2· 7 million participants. The Lancet, 378(9785), 31-40.

Duncan, G. E. (2006). Prevalence of diabetes and impaired fasting glucose levels among US adolescents: National Health and Nutrition Examination Survey, 1999-2002. Archives of pediatrics & adolescent medicine, 160(5), 523-528.

Tapia, P. C. (2006). Sublethal mitochondrial stress with an attendant stoichiometric augmentation of reactive oxygen species may precipitate many of the beneficial alterations in cellular physiology produced by caloric restriction, intermittent fasting, exercise and dietary phytonutrients:“Mitohormesis” for health and vitality. Medical hypotheses,66(4), 832-843.

Anson, R. M., Guo, Z., de Cabo, R., Iyun, T., Rios, M., Hagepanos, A., ... & Mattson, M. P. (2003). Intermittent fasting dissociates beneficial effects of dietary restriction on glucose metabolism and neuronal resistance to injury from calorie intake. Proceedings of the National Academy of Sciences,100(10), 6216-6220.

Mattson, M. P., & Wan, R. (2005). Beneficial effects of intermittent fasting and caloric restriction on the cardiovascular and cerebrovascular systems.The Journal of nutritional biochemistry, 16(3), 129-137.

Mattson, M. P. (2008). Dietary factors, hormesis and health. Ageing research reviews, 7(1), 43-48.

Halagappa, V. K. M., Guo, Z., Pearson, M., Matsuoka, Y., Cutler, R. G., LaFerla, F. M., & Mattson, M. P. (2007). Intermittent fasting and caloric restriction ameliorate age-related behavioral deficits in the triple-transgenic mouse model of Alzheimer's disease. Neurobiology of disease, 26(1), 212-220.