Intermittent Fasting and Time Restricted Feeding Benefit Explained, Resources

by Mike Mutzel



Key Takeaways from this Video:

01:30: Alternate-Day Fasting VS Continuous Energy Restriction
02:56: Alternate-Day Fasting group had greater energy deficit, yet didn't lost about the same amount of weight VS Continuous Energy Restriction group
03:40 Continuous Energy Restriction leads to a greater suppression in resting metabolic rate (RMR) long after the study compared to Alternate-Day Fasting
05:15 Fasting was first linked with health benefits in mice back in 1914
06:10: Your body doesn't have a “calorie sensor” per se; glucose, fatty acids, amino acids and their metabolites influence metabolism but we don't have a magical sensor for calories!
07:40: Energy absorption is different for everyone and may depend on the microbiome
11:50: Adaptive thermogenesis and weight-regain is more of a problem with calorie restriction


Reading Time: 5 minutes

Article Overview:

-Links and resources
-Images that explains how Intermittent Fasting (IF) works physiologically
-Brief history of how Intermittent Fasting (IF) came about
-Time Restricted Feeding (TRF) Overview
-Comparing intermittent fasting (IF) to continuous energy restriction (CER)  (aka calorie restriction or CR)

Interment fasting is all the rage nowadays. But humans have been fasting long before the internet popularized this effective approach to pivot your body into a fat burning state.

This post will review the benefits of fasting and time-restricted feeding (TRF), it's history and new studies that have compared intermittent fasting (IF) to calorie restriction.


In brief, both intermittent fasting (IF) and time-restricted feeding (TRF) are emerging as more viable alternatives to continuous energy restriction (CER)–meaning dieting, or eating less–because the body metabolically compensates by reducing key hormones that drive steady state metabolism (adrenaline, noradrenaline and thyroid hormones).




This is discussed in more depth by Sylvia Tara, PhD in her book, The Secret Life of Fat



Links and Resources that How Explain Fasting Works


I found this paper to be pretty revealing, especially the infographics detailing the physiology changed when one fasts.


Di Francesco, A., Di Germanio, C., Bernier, M., & de Cabo, R. (2018). A time to fast. Science (New York, N.Y.), 362(6416), 770–775.

Related: Detailed Intermittent Fasting Discussion with Dr. Jason Fung:


A Brief History of Fasting: Lessons Learned from Ramadan Fasting


Periodic fasting was described in various religious texts, including the Bible and Quaran. During the month of Ramadan for example, Muslims abstain from food and water from down until sunset for the entire holy month. The fast can last between nine and 19 hours, depending on the region in the world the follower of Islam resides. At dusk, the fast is broken and the last meal is consumed before dawn the next morning.


It’s worth noting that Islamic text allow exemptions for young children, pregnant and breast-feeding mothers, menstruating women, and folks with serious underlying medical complications. Although there are reports of childbearing Muslim mothers fasting for part of Ramadan, as the practice of fasting is culturally thought to contribute to enhanced psychological and social health of Muslims (1).  The practice of self-restraint is believed to purify the body and set one-up to do more good deeds in their community.


Calorie Restriction and Fasting Research Emerges in the Western Medical Literature

One of the first publications linking fasting to health improvements was recorded in 1914 by Peyton Rous of Rockefeller Institute for Medical Research. He observed that grafted tumors in underfed mice grew more slowly compared to ad libidum fed mice (3).

By the 1940s, researchers in the cancer field were confirming the early works by Rous, finding in animals that a 30 to 50 percent reduction in calorie intake was linked with a reduction in cancer growth in mice (4).

Multiple animal model studies were published between 1940 and 1960 making correlations with calorie restriction (CR), periodic starvation and metabolic improvements (5).

First Prolonged Fast in Humans Was Recorded

In the mid 1960's case studies started emerging detailing fat loss in obese humans who underwent prolonged fasts; ranging from 16 days to the longest recorded (to my knowledge) of 382 days (6,7).


Time-Restricted Feeding Emerges in the 1980s:

A modern day fasting alternative, time-restricted feeding (TRF), emerged from research in farming and agricultural studies in the 1970s.

In the mid 1970's researchers discovered that not just light exposure, but food and fasting, impacts biological rhythms (9). This is a big point of emphasis to consider when customizing a fasting protocol in your life.

Eating between say 10:00 AM and 6:00 PM is a classic  feeding window and good example of time-restricted feeding (TRF).  I generally recommend this type of approach food, just like light, entrains our body's circadian rhythms.


Meal consistency can help re-align other biological rhythms.


Related: How Time-Restricted Eating Can Enhance Sleep w/ Alessandro Ferretti


Mark Mattson and Valter Longo Move the Science of Fasting, and Time-Restricted Feeding (TRF) Forward:

In the 1990s and early 2000's multiple animal model studies show that both intermittent fasting (IF) and time-restricted feeding (TRF) offer multiple benefits with regards to cancer remission, neurodegeneration, diabetes and more.


In 2007 the first intermittent fasting (IF) clinical trial was published in humans (11). Interestingly, although all nine subjects who participated in this eight-week clinical trial were overweight, the  study was designed to see how alternate day fasting (ADF) would impact inflammatory markers linked to asthma and associated symptoms.


Just two weeks of alternate day fasting significantly reduced asthma symptoms in the test subjects. After eight weeks subject lost on average 8 percent of their starting body weight, had decreased triglycerides and lipids and noted reductions in a range of pro-inflammatory signaling molecules.


By 2009, several larger clinical trials emerge showing that alternate day fasting leads to weight loss in overweight humans (12). Other case studies reveal that fasting can be used alongside chemotherapy in cancer patients, reducing side-effects of chemotherapy (13).


influence of eating patterns on levels of glucose at ketones in the blood.
 Fig. 1. Examples of the influence of eating patterns on levels of glucose at ketones in the blood. Source: (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.


Intermittent Fasting VS Calorie Restriction:

One of the most highly contested topics on the web lately is controversy about calorie deficits VS intermittent fasting (IF) when it comes to fat loss.

If you’re part of the “energy balance” tribe, you argue that intermittent fasting (IF) is just a fancy way to get into a calorie deficit, which of course causes fat loss over time.

The “intermittent fasters,” like myself, say that the hormonal and epigenetic shifts that occur as an adaptation to periods of intermittent starvation offer metabolic benefits beyond just creating a energetic hole.

Scientists in Colorado published one of the first intermittent fasting VS calorie restriction studies, reporting similar weight loss between the both groups at the end of the eight-week study, even though the fasting group created an daily energy deficit of ~ 376 kcal/day. (If the calorie model holds true, the fasting group should have lost more weight than the VS calorie restriction group, but the between group difference was only one kilogram. (13)

What was most interesting about this study was the changes in resting metabolic rate (RMR) between the two groups. Although both groups observed a reduction in resting metabolic rate, the rate was reduced more than double in the calorie restriction arm vs the fasting arm.

Moreover, what was most interesting from this study was the 24-week follow up. Long after the study was over, subject in the fasting group lost nearly a pound and gained over two pounds of lean mass, while the calorie restricted group actually gain over two pounds of fat and only gained two pounds of lean mass.


Scientists in the UK tested Intermittent Fasting vs continuous energy restriction (low-calorie diets) in 27 male overweight subjects. Prior to the study, half of all subjects randomized to the Intermittent Fasting arm of the study were either had pre-hypertension or hypertension, after the study all but one subject no longer had hypertension.


“….our preliminary data suggest that the mode of ER (intermittent but severe v. modest continuous) may have differential cardiometabolic effects, which in turn could be important to long-term disease risk,” R. Antoni 2018 (14).




  1. Robinson, T., Dis, J. R. E., (2005). Each one is a doctor for herself”: Ramadan fasting among pregnant Muslim women in the United States. org, 15, S1–99– S1–103..
  2. Ahmad, S., Goel, K., Maroof, K., Goel, P., & Arif, M. (2012). Psycho-Social Behaviour and Health Benefits of Islamic Fasting During the Month of Ramadan. Journal of Community Medicine & Health Education, 2(178), 1–4.
  3. Rous, J. Exp. Med. 20, 433–451 (1914).
    12. T. B. Osborne, L. B. Mendel, E. L. Ferry, Science 45, 294–295
  4. Greenstein, J. P., & Haddow, A. (1954). Advances in cancer research. Academic Press Inc.
  5. Carlson, A. J., & Hoelzel, F. (1946). Apparent prolongation of the life span of rats by intermittent fasting. The Journal of Nutrition, 31(3), 363–375.
  6. Ball, M. F., Canary, J. J., medicine, L. K. A. O. I., 1967. (n.d.). Comparative effects of caloric restriction and total starvation on body composition in obesity. Am Coll Physicians
  7. Stewart, W. K., Fleming, L. W., & Robertson, P. C. (1966). Massive obesity treated by intermittent fasting. The American Journal of Medicine, 40(6), 967–986.

  8. Nelson, W., Cadotte, L., & Halberg, F. (2016). Circadian Timing of Single Daily “Meal” Affects Survival of Mice1:. Proceedings of the Society for Experimental Biology and Medicine, 144(3), 766–769.
  9. KRIEGER, D. T. (1974). Food and Water Restriction Shifts Corticosterone, Temperature, Activity and Brain Amine Periodicity. Endocrinology, 95(5), 1195–1201.

  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.

  11. Johnson, J. B., Summer, W., Cutler, R. G., Martin, B., Hyun, D.-H., Dixit, V. D., et al. (2007). Alternate day calorie restriction improves clinical findings and reduces markers of oxidative stress and inflammation in overweight adults with moderate asthma. Free Radical Biology & Medicine, 42(5), 665–674.

  12. Varady, K. A., Bhutani, S., Church, E. C., & Klempel, M. C. (2009). Short-term modified alternate-day fasting: a novel dietary strategy for weight loss and cardioprotection in obese adults. The American Journal of Clinical Nutrition, 90(5), 1138–1143.

  13. Catenacci, V. A., Pan, Z., Ostendorf, D., Brannon, S., Gozansky, W. S., Mattson, M. P., et al. (2016). A randomized pilot study comparing zero-calorie alternate-day fasting to daily caloric restriction in adults with obesity. Obesity, 24(9), 1874–1883.
  14. Antoni, R., Johnston, K. L., Collins, A. L., & Robertson, M. D. (2018). Intermittent v. continuous energy restriction: differential effects on postprandial glucose and lipid metabolism following matched weight loss in overweight/obese participants. British Journal of Nutrition, 119(5), 507–516.
  1. Hi Mike, I wanted to take probiotics after hip surgery to re establish my microbiome but I was concerned with doing more harm by inducing SIBO. How can I know if I’m getting the benefit without making myself sick? Also, now that the surgeons are using abbreviated courses of antibiotics (3 days) will the microbiome still be adversely affected? I realize you have to generalize because of individual factors such as the state of health prior to surgery and type of antibiotic, but any suggestions would be appreciated.
    Kindestregards, Mary Lou

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