Tag Archives: fasting

You Are When You Eat | The Paleo DietRenowned evolutionary biologist Theodosius Dobzhansky said “nothing in biology makes sense except in the light of evolution.”[1] Throughout our evolution, we have lived in daily cycles of light and dark. These cycles have led to the development of natural circadian rhythms that impact many aspects of our health and vitality.

Circadian rhythms are triggered by the bright light stimulus in the morning and darkness in the evening. The hypothalamus area of the brain – specifically the suprachiasmatic nucleus (SCN) – is the master regulator, synchronising the body’s circadian clock based on information it receives from photoreceptors in the eyes in response to light [2]. The impacts of circadian rhythm are wide-reaching;

Disruption of the circadian clock can have a big impact on the body’s ability to function optimally. Jet lag – that feeling of fatigue, disorientation and mental sluggishness after travelling through multiple time zones – is a classic example [3-6]

Unfortunately, the negative effects can be more serious than just a little sluggishness. The incidence of workplace injuries and traffic accidents increases when the clocks move forward in the spring [7, 8].

Experts are just starting to uncover the many potential ripple effects of circadian dysfunction on our health: from heart disease [9, 10] and cognitive decline [11, 12], to blood sugar dysfunction and increased diabetes risk [13]; to changes in body-fat storage and breakdown [14-16], reduced liver, pancreatic, and cardiac and skeletal muscle function [17-25].


Late-Night Eating & Circadian Rhythm

Today, there are many ancestral circadian mismatches with modern life. Late-night eating may be one of the most glaring incongruous elements. We’re in the midst of a weight gain and obesity epidemic with 70% of adults over the age of 20 in America are overweight or obese and 50% of the population now classified as pre-diabetic or diabetic.[26-27] A body of research is appearing showing that late-night eating may be a significant contributor [27-29].

A 2014 study of overweight and obese diabetics investigated the impacts of a late-night snack on their requirement for supplemental insulin. Subjects were divided into carbohydrate, whey protein, casein, or placebo groups. All groups required significantly more insulin after all late-night snacks, though the protein snack did compare more favourably to the carbohydrate snack [30]. These results confirmed a 2003 study on late-night eating and diabetics. This earlier study showed consistently higher blood sugar levels when snacking late at night, regardless of the macronutrient composition of the meal [31].

Why is late-night eating potentially so bad for us? One possible explanation is our circadian rhythms may prevent us from effectively managing food eaten later at night. There is evidence showing the thermic effect of food is reduced in the evening, due to the circadian regulation of insulin sensitivity, meaning your blood sugar and insulin response to carbs at night is more exaggerated than during the day [32].


Solutions for A Modern Circadian Mismatch

Our Paleolithic ancestors would’ve rarely (if ever) eaten after dark. Yet in today’s modern world, the light emitted from iPads, laptops, TVs and mobile devices make it far easier to stay up later at night. This presents a circadian mismatch to our evolutionary biological clocks which translates into more opportunity (and likelihood) to eat. If you’re struggling with weight gain, chronically high blood sugar, pre-diabetes or diabetes then shifting your focus to “meal-timing” can be a simple and highly effective part of the solution to improving your health.

To support a healthy circadian clock, implement the following “meal-timing” strategy:

  • Avoid eating late at night – consider abstaining from all food after 6:00 or 7:00 pm or ditch your late-night snacking while on the couch and try sipping on a herbal tea instead
  • Go for an evening walk, do some light stretching, or take a relaxing bath.


In my experience as a clinician, I see major progress in clients who decide to abstain from food in the evening. Once they get through the first few nights, the cravings plummet and it becomes much easier to ingrain the new habit.

Supporting your circadian clock with meal-timing strategies can be an “easy win” to restoring health and vitality [33]. It’s simple and highly effective. 


1. Gerhart-Hines, Z. and M.A. Lazar, Circadian metabolism in the light of evolution. Endocr Rev, 2015. 36(3): p. 289-304.
2. Guler, A.D., et al., Melanopsin cells are the principal conduits for rod-cone input to non-image-forming vision. Nature, 2008. 453(7191): p. 102-5.
3. Tapp, W.N. and B.H. Natelson, Circadian rhythms and patterns of performance before and after simulated jet lag. Am J Physiol, 1989. 257(4 Pt 2): p. R796-803.
4. Leloup, J.C. and A. Goldbeter, Critical phase shifts slow down circadian clock recovery: implications for jet lag. J Theor Biol, 2013. 333: p. 47-57.
5. Comperatore, C.A. and G.P. Krueger, Circadian rhythm desynchronosis, jet lag, shift lag, and coping strategies. Occup Med, 1990. 5(2): p. 323-41.
6. Vosko, A.M., C.S. Colwell, and A.Y. Avidan, Jet lag syndrome: circadian organization, pathophysiology, and management strategies. Nat Sci Sleep, 2010. 2: p. 187-98.
7. Coren, S., Daylight savings time and traffic accidents. N Engl J Med, 1996. 334(14): p. 924.
8. Varughese, J. and R.P. Allen, Fatal accidents following changes in daylight savings time: the American experience. Sleep Medicine, 2001. 2(1): p. 31-36.
9. Maemura, K., [Circadian rhythm and ischemic heart disease]. Nihon Rinsho, 2013. 71(12): p. 2124-9.
10. Marchant, B., Circadian rhythms and ischaemic heart disease. Br J Hosp Med, 1996. 55(3): p. 139-43.
11. Gehrman, P., et al., The relationship between dementia severity and rest/activity circadian rhythms. Neuropsychiatr Dis Treat, 2005. 1(2): p. 155-63.
12. Ancoli-Israel, S., et al., Variations in circadian rhythms of activity, sleep, and light exposure related to dementia in nursing-home patients. Sleep, 1997. 20(1): p. 18-23.
13. Afsar, B., Disruption of circadian blood pressure, heart rate and the impact on glycemic control in type 1 diabetes. Diabetes Metab Syndr, 2015. 9(4): p. 359-63.
14. Cincotta, A.H., et al., Circadian neuroendocrine role in age-related changes in body fat stores and insulin sensitivity of the male Sprague-Dawley rat. Chronobiol Int, 1993. 10(4): p. 244-58.
15. Wang, L. and S. Liangpunsakul, Circadian clock control of hepatic lipid metabolism: role of small heterodimer partner (Shp). J Investig Med, 2016. 64(7): p. 1158-61.
16. Gnocchi, D., et al., Lipids around the Clock: Focus on Circadian Rhythms and Lipid Metabolism. Biology (Basel), 2015. 4(1): p. 104-32.
17. Gerhart Hines, Z., et al., The nuclear receptor Rev-erbα controls circadian thermogenic plasticity. Nature, 2013. 503(7476): p. 410-413.
18. Bookout, A.L., et al., FGF21 regulates metabolism and circadian behavior by acting on the nervous system. Nat Med, 2013. 19(9): p. 1147-52.
19. Shostak, A., J. Meyer-Kovac, and H. Oster, Circadian regulation of lipid mobilization in white adipose tissues. Diabetes, 2013. 62(7): p. 2195-203.
20. Boden, G., et al., Evidence for a circadian rhythm of insulin secretion. Am J Physiol, 1996. 271(2 Pt 1): p. E246-52.
21. Degaute, J.P., et al., Quantitative analysis of the 24-hour blood pressure and heart rate patterns in young men. Hypertension, 1991. 18(2): p. 199-210.
22. Zambon, A.C., et al., Time- and exercise-dependent gene regulation in human skeletal muscle. Genome Biol, 2003. 4(10): p. R61.
23. Carter, R., et al., Non-alcoholic fatty pancreas disease pathogenesis: a role for developmental programming and altered circadian rhythms. PLoS One, 2014. 9(3): p. e89505.
24. Kettner, N.M., et al., Circadian Homeostasis of Liver Metabolism Suppresses Hepatocarcinogenesis. Cancer Cell, 2016. 30(6): p. 909-924.
25. Zhou, D., et al., Evolving roles of circadian rhythms in liver homeostasis and pathology. Oncotarget, 2016. 7(8): p. 8625-39.
26. CDC: Center for Disease Control & Prevention. Retrieved from – https://www.cdc.gov/nchs/fastats/obesity-overweight.htm
27. Menke, A., et al., Prevalence of and Trends in Diabetes Among Adults in the United States, 1988-2012. JAMA, 2015. 314(10): p. 1021-9.
28. Cleator, J., et al., Night eating syndrome: implications for severe obesity. Nutr Diabetes, 2012. 2: p. e44.
29. Gallant, A.R., J. Lundgren, and V. Drapeau, The night-eating syndrome and obesity. Obes Rev, 2012. 13(6): p. 528-36.
30. Colles, S.L., J.B. Dixon, and P.E. O’Brien, Night eating syndrome and nocturnal snacking: association with obesity, binge eating and psychological distress. International Journal of Obesity, 2007. 31(11): p. 1722-1730.
31. Kinsey, A.W., et al., Influence of night-time protein and carbohydrate intake on appetite and cardiometabolic risk in sedentary overweight and obese women. Br J Nutr, 2014. 112(3): p. 320-7.
32. Kalergis, M., et al., Impact of bedtime snack composition on prevention of nocturnal hypoglycemia in adults with type 1 diabetes undergoing intensive insulin management using lispro insulin before meals: a randomized, placebo-controlled, crossover trial. Diabetes Care, 2003. 26(1): p. 9-15.
33. Bo, S., et al., Is the timing of caloric intake associated with variation in diet-induced thermogenesis and in the metabolic pattern? A randomized cross-over study. Int J Obes (Lond), 2015. 39(12): p. 1689-95.
34. Mattson, M.P., et al., Meal frequency and timing in health and disease. Proc Natl Acad Sci U S A, 2014. 111(47): p. 16647-53.




Alzheimer's Disease and The Paleo Diet

One of the latest, fascinating publications from Science Daily, “Memory loss associated with Alzheimer’s reversed: Small trial succeeds using systems approach to memory disorders,” was called to my attention. The UCLA study suggests the potential lifestyle changes which may prevent or even reverse the devastation of Alzheimer’s disease. This study has relevance to both aging Paleo Dieters and to Paleo Diet enthusiasts who may have parents or grandparents at risk for Alzheimer’s disease.

First, let me point out that the study is anecdotal in nature, and until randomized controlled trials are carried out, it is premature to draw definitive conclusions. Yet the following recommendations have virtually no risks involved and a number of these recommendations occur spontaneously when people adopt contemporary Paleo Diets.  Let me address each of the 14 recommendations:

  1. Eliminating all simple carbohydrates, leading to a weight loss of 20 pounds;

The Paleo Diet is devoid of refined sugars and cereal grains, hence, it goes without saying that it is a lifetime program of eating that contains few simple carbohydrates.

  1. Eliminating gluten and processed food from her diet, with increased vegetables, fruits, and non-farmed fish;

Eliminating gluten from the diet may be therapeutic for the brain, nervous system, gut, immune and endocrine systems. Gluten containing grains upregulate one of the body’s own molecules called transglutaminase 2 which may be involved in the formation of molecules associated with brain lesions occurring in Alzheimer’s disease. There are absolutely no known nutritional or health risks with elimination of gluten containing grains (wheat, rye, barley) from your diet, and the health benefits are many.

I don’t think you will find nutritionists anywhere who do not recommend eating more fresh fruits and vegetables along with non-farmed fish.  These dietary recommendations are all mainstays of The Paleo Diet.

  1. To reduce stress, she began yoga;

Natural stress reducing activities such as yoga, exercise, walking, gardening, reading, interacting with friends, family and even pets should be encouraged for people of all ages.

  1. As a second measure to reduce the stress of her job, she began to meditate for 20 minutes twice per day;

Meditation has been demonstrated to produce multiple therapeutic effects for both mind and body.  Look no further than PUBMED for the scientific references.

  1. She took melatonin each night;

Improving melatonin metabolism has proven therapeutic effects upon sleep.  Less well appreciated is that the Paleo Diet is a low salt, low alcohol diet – both of which also are known to improve sleep and have beneficial effects upon melatonin metabolism.

  1. She increased her sleep from 4-5 hours per night to 7-8 hours per night;

Besides a low salt and alcohol diet, exercise can also improve sleep.

  1. She took methylcobalamin each day;

Normal melatonin metabolism required for proper sleep has frequently been demonstrated to be improved by vitamin B12 administration (either methylcobobalamin or cyanocobalamin). It should be noted that the Paleo Diet is naturally high in vitamin B12 because meat, eggs, fish and other animal products which are all excellent sources of vitamin B12 and consumed at virtually every meal.

  1. She took vitamin D3 each day;

The majority of elderly people in the US and elsewhere have been frequently shown to be deficient in vitamin D3, which really is not a vitamin at all, but rather a crucial hormone required for our body and mind’s optimal functioning.  As I have repeatedly stated in all of my popular books, if you cannot or do not get regular sunshine exposure, then this is one of the few supplements you will need to take on the Paleo Diet.

  1. Fish oil each day;

Fish oil is a concentrated source of two long chain omega 3 fatty acids (EPA and DHA), both of which have numerous therapeutic health effects upon the brain and nervous system. If you don’t eat fatty fish (salmon, mackerel, herring, sardines etc.) regularly then you will likely need to supplement with fish oil — one of the few supplements other than vitamin D that Paleo Dieters will need to consider.

  1. CoQ10 each day;

Natural concentrated sources of CoQ10 are meat, poultry and fish, which are staples in the Paleo Diet. There is little or no need to supplement with CoQ10 once you begin to eat meat poultry and fish at every meal.

  1. She optimized her oral hygiene using an electric flosser and electric toothbrush;

One of the little appreciated sources of chronic inflammation stems from our mouths. Numerous scientific studies show that plaque, gum disease and poor oral hygiene are known to increase systemic inflammation and be a risk factor for Alzheimer’s disease. Natural diets (like the Paleo Diet) which are high in soluble fiber from fresh fruits and vegetables and low in simple carbohydrates (refined sugars, refined grains) promote good oral health and reduced risk for dental caries.

  1. Following discussion with her primary care provider, she reinstated hormone replacement therapy that had been discontinued;

This is a controversial topic which will require an entire new article to address — stay tuned!

  1. She fasted for a minimum of 12 hours between dinner and breakfast, and for a minimum of three hours between dinner and bedtime;

From our non-published studies of meal frequencies in hunter-gatherers, at least two common patterns are apparent: 1) extended daily periods with little or no food, or 2) snacking throughout the day.

Pattern 1, frequently occurs when little or no food remains in “camp.” Consequently, men, women, and children set out typically in the morning to hunt, gather and forage for food. Their bounties are typically brought back to the home base and shared with everyone in a single large evening meal.

Frequently, foods are snacked upon as they are gathered. If sufficient food remains from the afternoon or evening meal, it is consumed continually for the next few days. These types of food procurement patterns produce patterns of fasting interspersed with patterns of snacking. Hence, it seems likely that fasting was a normal part of the human dietary pattern as hunter-gatherers.

  1. She exercised for a minimum of 30 minutes, 4-6 days per week.

As I have always said, any exercise is better than no exercise. And that exercise improves virtually all physiological measures including brain function.

In conclusion, I am supportive of the recommendations of this study. There are absolutely no health risks from following most of this advice, which dovetails nicely with Paleo dietary and health recommendations, yet the benefits may be great.


Loren Cordain, Ph.D., Professor Emeritus

Affiliates and Credentials