insights

Updated On: 11/19/2020

As part of cultural or religious traditions, humans have practiced periodic fasting for thousands of years. Only in the past century has much of the population had easy access to excess calories every single day throughout their lifespans. That access correlates with the onset of many chronic illnesses.

In addition to potentially assisting with chronic illness, appropriate fasting may help to build healthy resilience. Fasting has the potential to reduce some of the risk factors like obesity and metabolic syndrome¹ that have been deemed risk factors for worsened outcomes from COVID-19.² This is an area of great interest as the combined prevalence of prediabetes and diabetes is over 50% in the US population.³ A world where more people safely fast could improve overall population health.

“Fasting may also improve metabolic health [and] reduce obesity and type 2 diabetes. Since these metabolic diseases significantly increase the risk of so many other diseases, fasting may improve overall resilience substantially,” said Jason Fung, MD, who along with Dr. Alan Goldhamer both presented at at IFM’s Annual International Conference (AIC).

Drs. Goldhamer and Fung joined a lineup of world-renowned speakers at the 2020 Annual International Conference, where several lectures explored the latest research on dietary modifications, including intermittent fasting, fasting-mimicking diets, ketogenic diets, and more. Speakers include:

• Jason Fung, MD
• Alan Goldhamer, DC
• Stephen Phinney, MD
• Kurt Hong, MD, PhD

Cardiometabolic Connection

Intermittent fasting has been most studied in humans in relation to obesity and type 2 diabetes. Insulin sensitivity has long been known to improve after periods of fasting.⁴

Although care needs to be taken to monitor insulin levels and medications,⁵ intermittent fasting has been demonstrated to have significant benefits for patients with cardiometabolic conditions. In one randomized controlled trial, intermittent fasting significantly reduced HbA1c and improved glycemic control, and participants had very high rates of compliance.⁶

Intermittent fasting has also shown to be beneficial in a range of other cardiometabolic conditions:

• In a case series with three patients, type 2 diabetes was reversed and insulin discontinued due to therapeutic fasting.⁷
• During a study on Mormons in the US, periodic religious fasting was associated with a lower incidence of coronary artery disease.⁸
• In patients with coronary artery disease, routine periodic fasting has been correlated with a lower incidence of type 2 diabetes.⁹
• In patients with and without type 2 diabetes, intermittent fasting improved fatty liver index, a proxy for non-alcoholic fatty liver disease (NAFLD), significantly and rapidly.¹⁰
• Intermittent fasting in overweight women led to improved fasting insulin, insulin resistance, and inflammatory markers. The intervention was well tolerated over six months.¹¹
• A systematic review concluded that more research is needed, but intermittent fasting shows promise for helping to treat patients with obesity, and no serious adverse effects were documented.¹²

Timing & Considerations

Intermittent fasting can be undertaken in many ways, with different durations. With longer fasting times (likely over 24 hours), autophagy may be improved. During autophagy, the body undertakes housecleaning, removing damaged cells and pathogens, among other actions.¹³ This could be a beneficial process for improving immune function and helping patients with chronic inflammatory diseases,¹⁴ although research is still very much developing.

When considering fasting, the timing of the meal may also matter. The evidence base is nascent and well worth monitoring. For instance, emerging research suggests that evening fasting (skipping dinner) may be more effective than morning fasting (skipping breakfast),¹⁵ and that eating fewer meals during the day may reduce disease incidence.¹⁶ Meal timing affects circadian rhythms, and late night eating may contribute to obesity more than food consumed at other times of the day.¹⁶ This may in part be due to the diurnal rhythm of glucose tolerance, which peaks in the mornings; some evidence shows that peak is lowered by early-phase time-restricted feeding.¹⁷

Not everyone is a suitable candidate for fasting. As Dr. Goldhamer notes above, some preexisting conditions rule out fasting. Patients with a history of eating disorders also need to be carefully considered; in one study, along with other factors, fasting behavior was correlated with later emergence of anorexia nervosa in adolescent women.¹⁸ Dr. Hong adds, “For patients with chronic medical conditions, it is important to consult with their physicians before trying intermittent fasting to determine if adjustment in medications or lab testing may be needed.”

Ramadan fasting has provided a window into the potential effects of unmonitored fasting (usually prohibiting liquids as well) on diabetic patients. Hypo- and hyperglycemia is a concern, as is thrombosis,¹⁹ but researchers do conclude that type 2 diabetics likely can fast safely, with precautions.²⁰ High-quality studies on humans are still needed to determine long-term effects and to improve clinical confidence.²¹

Conclusion

There are many different ways to fast, and each patient may have a different response. To learn more about the therapeutic effects of fasting, download the Fasting: A Powerful Tool in Chronic Disease proceedings from AIC 2020. Speakers such as Drs. Fung and Goldhamer provide clinicians with the foundational understanding they need about the mechanisms, benefits, and risks of intermittent fasting and time-restricted feeding and how to implement fasting in their practices, whether that be via telemedicine or in a traditional clinic. AIC 2020 conference proceedings are available with eligible CME credit.

Learn More

References

1. de Cabo R, Mattson MP. Effects of intermittent fasting on health, aging, and disease. N Engl J Med. 2019;381(26):2541-2551. doi:1056/NEJMra1905136
2. CDC COVID-19 Response Team. Preliminary estimates of the prevalence of selected underlying health conditions among patients with coronavirus disease 2019 — United States, February 12–March 28, 2020. MMWR Morb Mortal Wkly Rep. 2020;69(13):382-386. doi:15585/mmwr.mm6913e2
3. Menke A, Casagrande S, Geiss L, Cowie CC. Prevalence of and trends in diabetes among adults in the United States, 1988-2012. JAMA. 2015;314(10):1021-1029. doi:1001/jama.2015.10029
4. Jackson IM, McKiddie MT, Buchanan KD. Effect of fasting on glucose and insulin metabolism of obese patients. Lancet. 1969;1(7589):285-287. doi:1016/s0140-6736(69)91039-3
5. Grajower MM, Horne BD. Clinical management of intermittent fasting in patients with diabetes mellitus. Nutrients. 2019;11(4):E873. doi:3390/nu11040873
6. Carter S, Clifton PM, Keogh JB. Effect of intermittent compared with continuous energy restricted diet on glycemic control in patients with type 2 diabetes: a randomized noninferiority trial. JAMA Netw Open.2018;1(3):e180756. doi:1001/jamanetworkopen.2018.0756
7. Furmli S, Elmasry R, Ramos M, Fung J. Therapeutic use of intermittent fasting for people with type 2 diabetes as an alternative to insulin. BMJ Case Rep. 2018;2018:bcr2017221854. doi:1136/bcr-2017-221854
8. Horne BD, May HT, Anderson JL, et al. Usefulness of routine periodic fasting to lower risk of coronary artery disease in patients undergoing coronary angiography. Am J Cardiol. 2008;102(7):814?819. doi:1016/j.amjcard.2008.05.021
9. Horne BD, May HT, Anderson JL, et al. Usefulness of routine periodic fasting to lower risk of coronary artery disease in patients undergoing coronary angiography. Am J Cardiol. 2008;102(7):814?819. doi:1016/j.amjcard.2008.05.021
10. Drinda S, Grundler F, Neumann T, et al. Effects of periodic fasting on fatty liver index—a prospective observational study. Nutrients. 2019;11(11):E2601. doi:3390/nu11112601
11. Harvie MN, Pegington M, Mattson MP, et al. The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: a randomized trial in young overweight women. Int J Obes (Lond). 2011;35(5):714?727. doi:1038/ijo.2010.171
12. Welton S, Minty R, O’Driscoll T, et al. Intermittent fasting and weight loss: systematic review. Can Fam Physician. 2020;66(2):117?125.
13. Bagherniya M, Butler AE, Barreto GE, Sahebkar A. The effect of fasting or calorie restriction on autophagy induction: a review of the literature. Ageing Res Rev. 2018;47:183-197. doi:1016/j.arr.2018.08.004
14. Deretic V, Levine B. Autophagy balances inflammation in innate immunity. Autophagy. 2018;14(2):243?251. doi:1080/15548627.2017.1402992
15. Nas A, Mirza N, Hägele F, et al. Impact of breakfast skipping compared with dinner skipping on regulation of energy balance and metabolic risk. Am J Clin Nutr. 2017;105(6):1351-1361. doi:3945/ajcn.116.151332
16. Paoli A, Tinsley G, Bianco A, Moro T. The influence of meal frequency and timing on health in humans: the role of fasting. Nutrients. 2019;11(4):E719. doi:3390/nu11040719
17. Jamshed H, Beyl RA, Della Manna DL, Yang ES, Ravussin E, Peterson CM. Early time-restricted feeding improves 24-hour glucose levels and affects markers of the circadian clock, aging, and autophagy in humans. Nutrients. 2019;11(6):E1234. doi:3390/nu11061234
18. Stice E, Gau JM, Rohde P, Shaw H. Risk factors that predict future onset of each DSM-5 eating disorder: predictive specificity in high-risk adolescent females. J Abnorm Psychol. 2017;126(1):38?51. doi:1037/abn0000219
19. V RA, Zargar AH. Diabetes control during Ramadan fasting. Cleve Clin J Med. 2017;84(5):352-356. doi:3949/ccjm.84a.16073
20. Badshah A, Haider I, Humayun M. Management of diabetes in Ramadan. J Ayub Med Coll Abbottabad. 2018;30(4):596-602.
21. Horne BD, Muhlestein JB, Anderson JL. Health effects of intermittent fasting: hormesis or harm? A systematic review. Am J Clin Nutr. 2015;102(2):464-470. doi:3945/ajcn.115.109553