Your body has an internal biological clock which decides when you sleep, eat, wake up, secrete hormones, process food and do many more functions.
The term circadian comes from the Latin word circa, meaning “approximately”, and diēm, meaning “day”. This daily rhythm is related to Earth’s rotation around its own axis which exposes all living beings to a 24-hour light-dark and temperature cycle.
Chronobiology is the science or study of the effect of time, especially rhythms, on living systems (including humans).
In the last several years many scientific studies have shown that the disruption of the circadian rhythm is related to a higher incidence of many conditions like Type 2 Diabetes, heart disease, inflammation, mood disorders, some cancers and obesity. In fact, rotating night shift–work has been called a probable carcinogen (cancer causing) by the World Health Organization. Night shift work and light at night(LAN) have been associated with a higher risk for breast cancer in women.
BASICS OF CIRCADIAN RHYTHM
Your body’s circadian rhythm is controlled by a circadian clock. The master clock is in the brain (Suprachiasmatic Nucleus SCN) and this controls all the other clocks in the other organs (peripheral clocks). Every cell in your body has this intrinsic clock and there are genes involved in the clock mechanisms. In fact, the clock is present even in cells in a petri dish in the lab!
Fig: Central clock in the Suprachiasmatic Nucleus in the brain and peripheral clocks in different organs.Zeitgebers: Light on retina and food intake.
Although circadian rhythms are built-in and self-sustained, external cues can modulate circadian rhythms.
What are the external cues (zeitgebers) modulating your circadian rhythm?
- Light falling on your eyes.
(Nerd Alert: Retinal melanopsin influences this. Loss of melanopsin retinal cells may be related to dysregulation of circadian rhythm in Alzheimer’s Disease )
- Intake of food
- External temperature.
Chrononutrition refers to food intake in coordination with your body’s daily rhythm. This concept implies that in addition to the type of food you consume, the time of ingestion is also critical for your health and well-being.
STUDY USING A SMARTPHONE APP:
In an interesting study reported in the journal Cell Metabolism (2015), Dr. Satchidananda Panda and Shubhroz Gill used a smartphone app to track eating patterns in healthy men and women who were living regular lives (not in a lab). The smartphone app was used to take pictures of everything that they ate or drank. This was done for 3 weeks.
WHAT DID THEY FIND:
- Most food (53.6%) was consumed after 6 PM, with less than 25% of caloric intake occurring before noon.
(My comments: Why is this important? This is related to your insulin secretion and insulin sensitivity. Lower Insulin sensitivity (IS) means higher body fat percentage and higher risk for Type 2 Diabetes and a whole host of diseases.) IS tends to be higher at breakfast than at lunch or dinner. So if most of your food intake occurs at a time of the day when you are less insulin sensitive, what can happen? You can become metabolically dysregulated and insulin resistant. This is a big problem in Asian Indians because diabetes and heart disease strikes them at least a decade before it does in the Western population. My dictum is “all Asian Indians are either pre-diabetic or diabetic until proven otherwise”)
- Only 25% of the meals occurred after >6 hours 41 min of fasting.
- About 90 % of people in the study ate for 14 hours 45 minutes in a day.
- In another part of the study, 8 people who ate for more than 14 hours in a day, were asked to reduce their eating duration to 10-12 hours and to follow the same pattern during week days and weekends.
What did they find?
- In 16 weeks of study duration the participants lost 3.27 kilograms of body weight!
- These 8 people on the time restricted eating (TRE) program reported better sleep, better energy levels and less hunger at bedtime.
- These people voluntarily agreed to stay on this eating pattern and they maintained their weight loss and sleep improvement and higher energy levels 1 year after they started on TRE. All this improvement from just restricting your eating from >14 hours to 10-12 hours! This is major!
Though the study did not mention testing for inflammatory markers or blood sugar and insulin, I am sure if they had measured, they would have found improvements in these biomarkers as well.
Weight loss is not a simple problem of calorie-in-calorie-out(CICO). I prefer to say fat loss because your weight includes your muscles and bones too. You don’t want to lose muscle! (More on this later).
- Download and use the app (REFERENCES SECTION) and track for yourself. You will get great insight.
- Implement Time Restricted Eating and see the difference in your health.
- Eat an early dinner: This is a big challenge in many Asian Indian homes but try moving your dinner time by half hour every week until you have your dinner around 6:30-7 PM everyday.May be difficult to change dinner time from 9:30 PM to 6:30 PM in one day.
- I know some of you do not reach home in time to have an early dinner. Maybe you can carry a second box of home cooked food to eat in the office or on the commute.
- If you reach home by 7 PM, have your dinner at that time instead of eating snacks then and save yourself from a late dinner just before you go to bed.
(Watch for post on “metabolic/social” jetlag ,later)
La Morgia, Chiara, et al. “Melanopsin-expressing retinal ganglion cells: implications for human diseases.” Vision research 51.2 (2011): 296-302. La Morgia, Chiara et al.
Melanopsin Retinal Ganglion Cell Loss in Alzheimer Disease.” Annals of Neurology 79.1 (2016): 90–109. PMC. Web. 18 Aug. 2016.
Gill, Shubhroz, and Satchidananda Panda. “A smartphone app reveals erratic diurnal eating patterns in humans that can be modulated for health benefits.”Cell metabolism 22.5 (2015): 789-798.
Time for Food: The Intimate Interplay between Nutrition, Metabolism, and the Circadian Clock Asher, Gad et al. Cell, Volume 161, Issue 1, 84 – 92
Saad, Ahmed, et al. “Diurnal pattern to insulin secretion and insulin action in healthy individuals.” Diabetes 61.11 (2012): 2691-2700.