Intermittent Fasting

Intermittent fasting is a generalized term used to describe cycles that alternate between periods of fasting and eating. It is important that you consult with your health care provider to evaluate the efficacy and safety of the various forms of intermittent fasting for your specific health concerns. Fasting is not recommended for frail individuals, pregnant or breastfeeding women, individuals with eating disorders, those with an underweight BMI, insulin-dependent diabetics, those with heart arrhythmias or low blood pressure. Again, it is very important to discuss the risks verses potential benefits with your Functional Medicine Provider.

There are a number of variations of fasting, but some of the more common approaches are as follows:

Time-Restricted Feeding (TRF) describes a shortened window of time when a person consumes calories from food and beverages. This is also called “prolonged nightly fasting” and usually extends a person’s typical overnight fast. For example a person may consume calories between the hours of 8:00 am-6:00 pm. Typically a stretch of 12-16 hours without eating fulfills the criteria for time restricted eating.

Alternate Day Fasting (ADF) also called fasting intervals, describes a cycle of fasting on one day and eating on the next day. On fasting days, people usually restrict calories to no more than 600 per day.

The 5:2 Diet: With this method you consume 500-600 calories on two non-consecutive days of the week, but eat normally the other 5 days.

Fast Mimicking Diet (FMD) describes a ketogenic diet that is typically followed for five days once a month. This 5-day, very low-calorie, low carbohydrate, structured food plan has been shown in clinical studies to improve body composition and numerous metabolic markers after three consecutive cycles (3 months.

Research is increasingly revealing that the various forms of intermittent fasting or time restricted eating have an impact on most all tissues and organs in our bodies.

If you are new to this practice, the most conservative and generally healthy pattern is to limit food intake to a 12-hour window and fast for 12 hours. For example, if your first meal of the day is at 7:00 am, you would finish your last meal of the day by 7:00 pm. Depending on your personal health goals and needs, a more aggressive and personalized program may be recommended and supervised by our staff.

Another critical component of intermittent fasting is to finish your last meal of the day at least 2-3 hours prior to bedtime. This way our food is fully digested before we go to sleep and our gastrointestinal (GI) system is allowed an optimal healing and restorative rest as well.

Giving the body and the digestive system a rest from food and digestive processes allows “autophagy” or cellular house cleaning. Autophagy is a cleansing process our body uses to take apart aged damaged cells and replace them with new fully functioning cells. This can only happen when the body is at rest.

When we think of the how to best care for our bodies and maximize our health, it helps to keep in mind certain principles that are consistently true across all of creation that serve to create balance, health and orderly function.

One foundational principle would include the need for rhythms and cycles. We can “see” very clearly in the external universe, the need for order, structure and rhythms. There is day, night, seasons, sunshine and rain, growth, harvest etc.

Our bodies operate as a complex universe of trillions of biochemical reactions occurring minute by minute that functions best when we honor the natural rhythms of our biology. All body systems operate on a circadian rhythm and require alternating activity and rest cycles for maximum function and restoration. Our body systems also work best with order and structure verses chaos. This is particularly important for our gastrointestinal (GI) system. Intermittent fasting is an eating pattern that respects rhythms of eating and rest/fasting.

The more consistent we can become with our meal pattern within the eating window allows our blood sugar and insulin secretion to regulate. This will go a long way in decreasing inflammation in our body, as inconsistent spikes in blood sugar and insulin levels is one of the major contributors to inflammation.

Keep in mind maintaining a consistent blood sugar/insulin pattern and resulting lowered baseline inflammation will also increase the strength or our immune system to regulate itself and fight off infections appropriately. A consistent, controlled pattern of eating such as intermittent fasting, incorporating nutrient-rich anti-inflammatory whole real foods is one of the most powerful ways to ward off chronic disease such a diabetes and also fight off acute infections such as Covid-19.

General Recommendations for Fasting

• Drink plenty of filtered water on fasting days. Your Functional Medicine Provider may also recommend electrolytes or other supplements personalized for you.
• High-intensity exercise is not recommended while fasting. Walking, yoga, or other light-intensity activity is preferred.
• Be aware of your movement, as you may feel dizzy or lightheaded, especially when first starting a fast.
• Prioritize whole, unprocessed, nutrient dense foods, especially as you are limiting your intake on fasting days.
• Listen to your body and stop fasting if you feel unwell and call your Functional Medicine Provider.

We invite you into AustinMD to visit with one of our providers to learn which option is safest for you and fits your unique health needs.

1. Patterson R, et al. Intermittent Fasting and Human Metabolic Health. J Acad Nutr Diet. 2015;115(8):1203–1212. doi:10.1016/j.jand.2015.02.018
2. Wei M, et al. Fasting-mimicking diet and markers/risk factors for aging, diabetes, cancer, and cardiovascular disease. Sci Transl Med. 2017;9(377):eaai8700. doi:10.1126/scitranslmed. aai8700
3. Mattson M, Longo V, Harvie M. Impact of intermittent fasting on health and disease processes. Ageing Res Rev. 2017;39:46–58. doi:10.1016/j.arr.2016.10.005
4. de Cabo R, Mattson MP. Effects of intermittent fasting on health, aging, and disease. N Engl J Med. 2019;381(26):2541–2551. doi:10.1056/NEJMra1905136
5. Trepanowski J, Kroeger C, Barnosky A, et al. Effect of alternate-day fasting on weight loss, weight maintenance, and cardioprotection among metabolically healthy obese adults: a randomized clinical trial. JAMA Intern Med. 2017;177(7):930–938. doi:10.1001/jamainternmed.2017.0936

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