The Benefits of Intermittent Fasting

The Benefits of Intermittent Fasting

You have likely heard of intermittent fasting, but you may have some confusion about exactly what it means to follow an intermittent fasting diet. The goal of intermittent fasting is to give your digestive system a break on a regular basis. For some, that means creating a fasting plan that focuses on a specific eating window for meals. Intermittent fasting can be as formal or as informal as you like and you don’t have to subscribe to a single fasting plan 100% of the time. 

Research shows that intermittent fasting is more than a fad, it can be a healthy eating plan that helps reduce unwanted body fat, maintain body weight, balance blood glucose, improve heart health, and is a powerful tool for preventing and reversing chronic disease. But, how do you do it? And, is it safe?

Types of Intermittent Fasting (IF)

Many diet plans focus on daily calories and what to eat, but IF is all about timing and when you eat. You have likely heard of time-restricted eating, alternate-day fasting, the fasting-mimicking diet, or other methods of intermittent fasting. Here we’ll break down some of the most common methods of intermittent fasting: 

• 16:8 time-restricted eating is highly effective. This method involves fasting for 16 hours between dinner and your first meal the next day, limiting eating to an eight-hour eating window. If you’re not ready to start with a 16-hour fasting window right off the bat, start by aiming for 12 hours between dinner and breakfast, then 13 hours, and so on until you hit the 16-hour mark. This type of fasting plan works well for people's busy schedules since many rush out the door (or into home offices) first thing in the morning and don’t have time to linger over breakfast. An eight-hour eating window has been found to improve mitochondrial function, detoxification, and reduce inflammation.⁽¹⁾ Some individuals experience better cognitive function, focus, and sleep, less pain, faster recovery from injuries, improved blood sugar and insulin levels, weight loss, and decreased systolic blood pressure. ^{(2, 3, 4, 5, 6, 7, 8)} 
• 24-hour fasts are another option. You can do a 24-hour fast as little as once or twice a month or as much as once per week depending on your own body’s response. On non-fasting days you can resume your normal, healthy diet. Make sure to stay very well-hydrated if you choose to experiment with this and do it at a time when you have low physical and emotional demands in case you need to rest. The shift in metabolism from glucose to fat may be most pronounced after about 18 hours of fasting, which may benefit those wanting to lose body fat or balance weight. Please seek medical advice from your functional medicine clinician, dietitian, or nutritionist if you have health conditions that may be affected, have any adverse effects, or are taking any medications that might need to be monitored or adjusted with fasting.
• Fasting mimicking diet is another tool you can use for a deeper metabolic reset. The fasting mimicking diet (FMD) is a low-calorie fasting plan that follows a 5-day eating program, done once per month for three months. For optimal results, one additional round of the 5-day eating pattern can be done quarterly throughout the year. As the name suggests, FMD mimics the physiological state of fasting. Simply put, it tricks your body into believing that you are fasting but you are actually eating selected foods. This pattern was created by Professor Valter Longo, and it consists of low-protein, low-carb, and high-fat meals. According to Longo, a fasting-mimicking diet promotes health in a way similar to other fasting plans.

Health Benefits of Intermittent Fasting

Intermittent fasting can provide a number of measurable health benefits. It creates a metabolic switch that affects both the body and the brain. Intermittent fasting can be protective against a variety of chronic illnesses including heart disease, obesity, age-related neurodegenerative disorders such as dementia and Alzheimer's, many cancers, and type 2 diabetes to name a few. Intermittent fasting is also particularly good at reducing inflammation and improving health conditions associated with inflammation, including arthritis, asthma, MS, and Alzheimer's. ^{(9, 10, 11)}  

Other benefits of fasting include: 

• Enhanced cognition: less brain fog and enhanced focus and processing speed.
• Increased energy, especially in the morning.
• Improved gut function: less bloating, better digestion.
• Balanced blood sugar: fewer cravings, more stable energy levels throughout the day, and balanced insulin levels.

• Strengthened cardiovascular health: improved blood pressure, cholesterol, and resting heart rate.

When to Avoid Intermittent Fasting 

There are some people for whom a fasting diet is not appropriate:

• Underweight individuals. Eating breakfast is important for those who need to gain weight or have trouble maintaining weight.
• Women seeking to optimize their fertility. You want to create an environment of nutrient abundance to optimize fertility, and IF creates a temporary nutrient deprivation state.
• Individuals with adrenal or hypothalamic pituitary adrenal (HPA) axis dysfunction, particularly those with elevated cortisol levels. Fasting can raise cortisol, especially when you’re drinking caffeinated beverages, such as black coffee, during the fast.
• Individuals who are suffering from an eating disorder, or may have had an eating disorder or disordered eating in the past.
• Women who are pregnant or breastfeeding.

Intermittent Fasting for Beginners

The 16:8 time-restricted eating is suitable for most beginners, but can also be worked up to gradually. After about 12 hours of fasting, the body switches to ketones for fuel. After this time point, processes such as autophagy and mitophagy upregulate. Autophagy involves general cellular cleanout and mitophagy is the process by which the function of our mitochondria (our cell batteries) is optimized.

Intermediate and advanced users might consider a once-weekly 24-hour fast, where just water and electrolytes are consumed. Individuals for whom 16:8 fasting is contraindicated (see list above) should not do this type of fasting plan as it can increase stress in those with hypervigilant nervous systems.

While intermittent fasting can help prevent and reverse chronic disease, it is important to seek medical advice from your doctor or dietitian before starting. Extended periods without food, such as 24-, 36-, 48-, and 72-hour fasting periods, are not necessarily better for you and may be dangerous. Going too long without eating might actually encourage your body to start storing more fat in response to starvation. If you are interested in starting a fasting plan, speak to your functional medicine clinician about which one is right for you and how to begin safely. 

References 

1. Zhao, Y., Jia, M., Chen, W., & Liu, Z. (2022). The neuroprotective effects of intermittent fasting on brain aging and neurodegenerative diseases via regulating mitochondrial function. Free Radical Biology and Medicine, 182, 206–218. https://doi.org/10.1016/j.freeradbiomed.2022.02.021
2. Li, L., Wang, Z., & Zuo, Z. (2013). Chronic intermittent fasting improves cognitive functions and brain structures in mice. PLoS ONE, 8(6). https://doi.org/10.1371/journal.pone.0066069
3. Gudden, J., Arias Vasquez, A., & Bloemendaal, M. (2021). The effects of intermittent fasting on brain and cognitive function. https://doi.org/10.20944/preprints202108.0528.v1
4. Ooi, T. C., Meramat, A., Rajab, N. F., Shahar, S., Ismail, I. S., Azam, A. A., & Sharif, R. (2020). Intermittent fasting enhanced the cognitive function in older adults with mild cognitive impairment by inducing biochemical and metabolic changes: a 3-year Progressive Study. Nutrients, 12(9), 2644. https://doi.org/10.3390/nu12092644
5. Sibille, K. T., Bartsch, F., Reddy, D., Fillingim, R. B., & Keil, A. (2016). Increasing neuroplasticity to bolster chronic pain treatment: a role for intermittent fasting and glucose administration? The Journal of Pain, 17(3), 275–281. https://doi.org/10.1016/j.jpain.2015.11.002
6. Caron, J. P., Kreher, M. A., Mickle, A. M., Wu, S., Przkora, R., Estores, I. M., & Sibille, K. T. (2022). Intermittent fasting: potential utility in the treatment of chronic pain across the clinical spectrum. Nutrients, 14(12), 2536. https://doi.org/10.3390/nu14122536
7. Albosta, M., Bakke, J. (2021) Intermittent fasting: is there a role in the treatment of diabetes? A review of the literature and guide for primary care physicians. Clinical Diabetes & Endocrinology 7(3). https://doi.org/10.1186/s40842-020-00116-1
8. Klempel, M.C., Kroeger, C.M., Bhutani, S. et al. (2012) Intermittent fasting combined with calorie restriction is effective for weight loss and cardio-protection in obese women. Nutrition Journal 11, 98. https://doi.org/10.1186/1475-2891-11-98
9. Gudden, J., Arias Vasquez, A., & Bloemendaal, M. (2021). The effects of intermittent fasting on brain and cognitive function. https://doi.org/10.20944/preprints202108.0528.v1
10. 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.arres.2021.100026
11. Impact of intermittent fasting on health and disease processes. (2022). The Intermittent Fasting Revolution. https://doi.org/10.7551/mitpress/13461.003.0006