WHAT IS INTERMITTENT FASTING?

Intermittent Fasting: These two words have gained much traction over the past few years.  Physicians, celebrities, and many others have created a revitalized interest in this concept. This is evident by Terry Crews’ discussions on incorporating intermittent fasting into his weight lifting routine, to Dr. Jason Fung’s book, The Obesity Code, and the recent case series in the British Medical Journal describing the therapeutic use of intermittent fasting in the treatment of diabetes. Experts agree that this eating regimen may result in favorable metabolic changes and, thus, improve human health. Importantly, evidence suggests intermittent fasting regimens, assuming the individual does not have contraindications, are safe in terms of both physical and mental health in normal weight, overweight or obese healthy adults. But what exactly is intermittent fasting?

Intermittent fasting refers to voluntary abstinence from food and calorie-containing beverages for a predefined period of time.  A variety of formats can be applied.  Many intermittent fasting protocols do not specify what to eat or drink, rather they instruct participants when to consume calories. The most popular types of intermittent fasting include:

• TIME-RESTRICTED FASTING, which involves unlimited energy intake within specific time frames, followed by regular, extended fasting intervals (e.g. 16:8, 18:6).
• ALTERNATE-DAY FASTING (ADF), which involves alternating fasting days, that is days with no energy containing foods and drinks, and eating days.
• MODIFIED FASTING REGIMENS, which involves consumption of 20–25 % of energy needs on fasting days.
• RELIGIOUS FASTING, such as Ramadan and other religious fasts. ¹

Time-restricted fasting, or periodical fasting, is a very commonly applied approach to intermittent fasting. One example is the 16:8 fasting protocol. 16:8 refers to the abstention from energy containing foods or drinks for 16 hours followed by eight hour feeding periods. Similarly, 18:6 fasting protocol means 6 hours of feeding with 18 hours of fasting. For instance, 16:8 can be simply applied by skipping breakfast and eating between 11 am and 7 pm, followed by 16 hours of fast.

Evidence suggests alternate-days fasting protocol from three weeks to 3 months can lead to successful body weight reduction, with decrease in total body fat, as well as blood lipid levels. These benefits can be achieved not only in obese and overweight, but in normal-weight individuals as well.  Whole-day fasting protocols lasting from 3 to 6 months can also reduce body weight and fat with improvements in blood lipids status. ²

An example of a modified fasting regimen represents the basis for the popular 5:2 diet.  The 5:2 diet involves eating nutritiously for five days out of the week. On the other two (typically nonconsecutive) days, followers of this approach consume 500-600 calories a day.  This is my least favorite approach, due to the focus on caloric restriction; however, many people find success with this practice.  Additionally, it may serve as an introduction to other fasting protocols, particularly if one has difficulty with other methods.

While human studies have mostly focused on the impact of intermittent fasting on body weight and fat, animal studies indicated further health benefits. To be more specific, studies on laboratory animals have shown that intermittent fasting beneficially affects various health indices and improves outcomes of a wide range of diseases. These include metabolic disease, e.g. diabetes and cardiovascular disease; cancers and neurological disorders, such as stroke, Alzheimer and Parkinson diseases. ³

Taking a closer look at intermittent fasting protocols, one can easily assume that appetite would be multiplied after an extended period of fasting. Still, research says otherwise. A group of researchers conducted an interesting trial involving obese healthy volunteers. After an overnight fast, participants were divided into two groups: one skipping breakfast, and the other getting a typical breakfast rich in carbohydrates. Three hours later both groups were served with an ad libitum (no restriction in amount) pasta lunch. Lunch intake between the two groups was compared, as well as the level of appetite controlling hormones. The results revealed no difference in quantity of food consumed for lunch. In other words, extended morning fasting did not cause compensatory intake during lunch nor it increased the appetite in the afternoon.⁴ 

While intermittent fasting offers many health benefits, proper precautions should be employed prior to starting any fasting protocol. Without proper attention to liquid intake and electrolytes, fasting can result in dehydration, electrolyte abnormalities, or other stressors.  As mentioned previously, certain medical conditions, such as diabetes for example, requires strict monitoring by a healthcare professional familiar with medication adjustment during the fasting period.  It is always better to seek advice from medical professional, especially when undertaking extended fasting protocols such as alternate day fasting (not consuming food more than 24-36 hours or longer) or in the presence of medical conditions.

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REFERENCES

1. Patterson RE, Sears DD. Metabolic Effects of Intermittent Fasting. Annu Rev Nutr. 2017;37:371-393. https://www.ncbi.nlm.nih.gov/pubmed/28715993
2. Tinsley GM, La Bounty PM. Effects of intermittent fasting on body composition and clinical health markers in humans. Nutr Rev. 2015;73(10):661-74. https://www.ncbi.nlm.nih.gov/pubmed/26374764
3. Mattson MP, Longo VD, Harvie M. Impact of intermittent fasting on health and disease processes. Ageing Res Rev. 2017;39:46-58. https://www.ncbi.nlm.nih.gov/pubmed/27810402
4. Chowdhury EA, et al. Effect of extended morning fasting upon ad libitum lunch intake and associated metabolic and hormonal responses in obese adults. Int J Obes (Lond). 2016;40(2):305-11 https://www.ncbi.nlm.nih.gov/pubmed/26278005

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DISCLAIMER: The advice on this page is not meant to replace or represent medical advice. This is nutritional advice, which is NOT the same as medical advice. Before any weight loss endeavor, the consultation of an experienced health care provider is a must. As a general rule, the following individuals should not participate in fasting:

• Diabetics-particularly those on insulin
• Lactating women
• Pregnant women
• Individuals with a history of eating disorders
• Children under the age of 18

This list is not all-encompassing; therefore, you should consult your healthcare provider before any new dietary or exercise approach.

Interaction through this blog’s associated social media accounts, podcasts, and other venues associated with The Fasting Doctor does not constitute a patient-physician relationship. Likewise, it does not constitute medical advice. By continuing to access this blog or related resources, you acknowledge and agree that the content and contributors are not liable for your personal use of dietary and wellness advice found in our contents. You acknowledge our recommendation to consult your care provider before utilizing our nutritional information.

For more information, please contact me at info@thefastingdoctor.com!