REVERSE FASTING

Many popular intermittent fasting protocols consist of eating windows between noon-8pm, thus delaying breakfast until the late morning or early afternoon.  While this provides participants an opportunity to experience a period of fasting, questions are beginning to emerge as to the effects of nighttime eating.  The circadian rhythm, our natural biological clock, sends various hormonal signals that create differences in functioning during the day versus the night. “Reverse fasting”, a term popularized by Dr. Amy Shah, gets to root question regarding when is the best time of day to conclude the consumption of meals.

REAL LIFE EXAMPLES

During residency, one of my favorite night shift nurses, Cassie, almost NEVER ate during her shift.  One night, as I was snacking away, I asked her why she declined to eat during her shift.  She flashed a huge smile and stated, “Because I don’t want to gain weight.”  I laughed it off.  However, Cassie was and still is, very in shape.  At the time, I didn’t think much of her eating pattern, yet she essentially practiced intermittent fasting without putting a name to it.  Essentially, Cassie followed a “reverse fasting” protocol without the need to label it.  She simply abstained from eating during the period our bodies are not designed for food consumption.  I recently connected with Cassie to see if she remembered our conversation.  She didn’t, which isn’t surprising given my talent for remembering random items.  However, she did confirm that she never ate during a night shift.  Essentially, she is a reverse faster.

Fast-forward to 2017 and my indoctrination into the world of intermittent fasting.  As I learned more of the physiologic mechanisms of fasting and the purported benefits, I began to notice increasing examples of this practice across many people in my life, most notably, my 102-year-old, Great Aunt, Elva.  In addition to following a plant-based lifestyle for the majority of her life, my aunt consumes her meals at 10 am and 4 pm daily.  In the evening, she may have a glass of tea or another unsweetened beverage, but by and large, the majority of her eating is completed by sunset.  Her cognitive function parallels that of a 20-year-old, she not only meets, but also exceeds in the performance of activities of daily living, and enjoys health that is superior to that of the general population as a whole.  Again, she didn’t have to create a name for this practice.  She eats when she is hungry.  Aunt Elva does not allow the exogenous and false cues of society skew her body into eating outside of the times naturally designed to eat.  She is in sync with her biological clock.

POTENTIAL MECHANISMS

When taking a closer look at our circadian rhythm, cues and stimuli from our surroundings provide feedback to our hypothalamus, which in turn signals several different functions including, our reproductive system, inflammatory markers, metabolism, and a host of other processes.  It is hypothesized that a misalignment of food consumption with our natural circadian clock is a risk factor for weight gain, diabetes, and other metabolic disease states (1).  Research among night-shift workers seems to support this concept.  Resting energy expenditure is lowest during the night period and highest during the afternoon(2).  This means the body will utilize available energy to a greater degree during the waking hours, thus having less energy available for excess storage.  Macronutrient utilization is most significant during the morning hours and lowest in the evenings, thus demonstrating another potential mechanism of unintentional weight gain (2).

Another study demonstrated decreases in total daily energy expenditure and reduced energy expenditure when participants converted from a daytime to night shift schedule (3).  According to our biologic clock, the melatonin surge is indicative of the beginning of the physiologic night.  A fascinating study involving 110 participants between the ages of 18-22 demonstrated an increase in body fat composition compared with lean individuals when mealtime consumption occurred after the start of our biologic night (4).   This effect persisted AFTER controlling for caloric intake, physical activity, gender, sleep duration, and meal composition(4)! Still, further studies have demonstrated greater weight loss potential when the “main meal,” or meal with the highest caloric value, occurs during breakfast as opposed to dinner.  Remember, these results persist DESPITE having the same total caloric intake in 24 hours (5).  There is a plethora of evidence suggesting our bodies are far more complex concerning energy balance, weight gain, and weight loss than the “calories in/out” approach.

Aside from weight gain, circadian disruption appears to play a role in underlying inflammation, perhaps contributing to gastrointestinal, cardiovascular, and immune functions (6, 7).  Not only does inadequate sleep affect our circadian rhythm, but feeding times also play a significant role in this disruption.  While animal models are essential to understanding disease in humans, a common critique of animal studies, particularly on rodents, is that a mouse is not synonymous with human life.  I want to point out that many of the above studies WERE performed on human volunteers.  The aforementioned studies lend scientific evidence to the real-life observations noted in the introduction.  This is not to discount the thousands of individuals who practice intermittent fasting around the globe in which their eating window ends after dark.  However, I would like to introduce the notion that perhaps MORE could be obtained from intermittent fasting by tapping into our natural circadian rhythm at least part of the time.

If your current fasting window allows for the regular consumption of food after sunset, you are potentially shortchanging yourself of the maximum fasting benefit.

HOW TO BEGIN

The term, “reverse fasting” consists of ending the eating window earlier in the day to allow the body to rest during nighttime hours.  In turn, this enables breakfast eaters to consume their first meal near 9 or 10 am and provides a fasting period of at least 16 hours depending on sunset.  The key is to consume food during the day when the sun is visible and conclude intake by sunset.

1. DO WHAT YOU CAN. If you prefer to fast for less than 16 hours, IT IS OKAY.  We don’t do “fast” shaming here. Merely breaking the habit of nighttime eating, decreasing grazing throughout the day, and minimizing your intake of processed carbohydrates in preference for REAL, whole foods will benefit you tremendously. A study of participants during Ramadan demonstrated decreased markers of inflammation (8).  For those unfamiliar with Ramadan fasting, participants abstain from food from sunrise to sunset.  Depending on the time of year, the fasting window is varied from 10-14 hours.  Therefore, if you are new to intermittent fasting, try fasting from SUNSET to SUNRISE to take advantage of your natural circadian rhythm.  Given the benefits with fasting for a minimum of 12 hours, just starting with ending night eating can create health benefits.  This will result in a longer eating window during the summer and a shorter eating window in the winter.
2. CHANGE UP YOUR SCHEDULE!  Our bodies are intelligent.  We can adapt to anything that becomes routine for too long.  Perhaps, you are an avid faster but prefer the most substantial meal of the day during the evening periods.  Why not change it up two to three times a week?  Set aside a few days where your morning or early afternoon meal is the largest of the day and consume your last meal by sunset (or 6 pm if sunset is not feasible).  This may be particularly helpful when in the midst of a weight loss plateau.
3. FOCUS ON REAL FOODS DURING THE EATING WINDOW.  Whether you are plant-based, keto, low carb, or a whole foods type of person, MANY ways of eating throughout the world have demonstrated health benefits, except the “Western” diet high in processed foods. Avoid eating high starch foods, processed/refined carbohydrates (carbs in a box, even if it’s labeled “heart healthy”), and focus on whole foods.  It is up to you to determine which ratio of protein to real fruits and vegetables is sustainable in the long term.  However, the reduction of processed carbs is central to any healthy diet.  Start there.  Once you have that down, you can experiment more with which nutrients allows your body to perform optimally.
4. GIVE IT A TRY (assuming you’ve discussed your plans with a healthcare provider).  Don’t worry about getting it right on the first try.  Pick an initial step to focus on and build upon the model in the days, weeks, months, and YEARS to come. Remember, this is a LIFESTYLE change. Not a fad. Fads fade. Health and longevity remain. Just ask my aunt!

Have you personally experienced the benefits of reverse fasting?  Are you ready to give it a try?  If so, I invite you to share your experiences via Instagram or Facebook with the #TwoWeeksOfReverseFasting.  Hopefully, after a few weeks, eating during the night will become the exception, not the rule.

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REFERENCES

1. Engin A. Circadian Rhythms in Diet-Induced Obesity. Adv Exp Med Biol. 2017;960:19-52.
2. Zitting KM, Vujovic N, Yuan RK, Isherwood CM, Medina JE, Wang W, et al. Human Resting Energy Expenditure Varies with Circadian Phase. Curr Biol. 2018;28(22):3685-90 e3
3. McHill AW, Melanson EL, Higgins J, Connick E, Moehlman TM, Stothard ER, et al. Impact of circadian misalignment on energy metabolism during simulated nightshift work. Proc Natl Acad Sci U S A. 2014;111(48):17302-7.
4. McHill AW, Phillips AJ, Czeisler CA, Keating L, Yee K, Barger LK, et al. Later circadian timing of food intake is associated with increased body fat. Am J Clin Nutr. 2017;106(5):1213-9.
5. Garaulet M, Gomez-Abellan P. Timing of food intake and obesity: a novel association. Physiol Behav. 2014;134:44-50.
6. Codoner-Franch P, Gombert M. Circadian rhythms in the pathogenesis of gastrointestinal diseases. World J Gastroenterol. 2018;24(38):4297-303.
7. Pagel R, Bar F, Schroder T, Sunderhauf A, Kunstner A, Ibrahim SM, et al. Circadian rhythm disruption impairs tissue homeostasis and exacerbates chronic inflammation in the intestine. FASEB J. 2017;31(11):4707-19.
8. Aksungar FB, Topkaya AE, Akyildiz M. Interleukin-6, C-reactive protein and biochemical parameters during prolonged intermittent fasting. Ann Nutr Metab. 2007;51(1):88-95.

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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
• Pregnant women
• Individual 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 Fasting Work Girl 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.