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Circadian System, Meal Timing, and Metabolism

Circadian System, Meal Timing, and Metabolism 



Part 1: Circadian Systems


            Last weekend, I attended the Food and Nutrition Conference and Expo in Chicago. Not only did I meet lots of passionate and driven Registered Dietitians and students, but I also learned a lot through continuing education sessions. One of my favorite sessions I attended was on circadian systems and meal timing. In part one of this blog, I will summarize what I learned about circadian rhythms. Next week, I will go into more detail about meal timing.


            Virtually every cell in our body has an “internal clock”. As humans, we were made to run on a 24 hour cycle. When the light bulb was invented, it made it possible for us to continue working into the night. The first problem this causes is short/disrupted sleep. A commonly known fact is that people who sleep less are more likely to gain weight. We think that this is because the more you are awake, the more you eat, but there’s actually more to it than that. When you shorten sleep, you change your metabolism. Ghrelin (the hunger hormone) levels increase and leptin (the satiety hormone) levels decrease due to shifts in sleep patterns. These hormonal shifts are associated with an increased risk for type 2 diabetes. Also, if you’re awake for longer, being awake requires more energy.


            What about shift work? Working night shifts on some days and sleeping all day on some days, but not on days off also disrupts your metabolism. Research shows that it takes one full day to adjust to one hour of a time zone difference (think daylight savings time changes or traveling to Europe for vacation). This causes a circadian misalignment. Working night shifts, but not every day is like taking a trip to Tokyo once a week, and likewise it can cause metabolic disorders (like diabetes, mentioned above).


            So how do we fix our circadian systems? Most importantly, we should try to get enough sleep. 7-9 hours per night is the recommended amount for adults (children and adolescents under the age of 18 require more, depending on age). Going to sleep and waking up around the same time every day can also help. Some tips for achieving better sleep cycles and getting better sleep are: avoid stimulants and alcohol 3-4 hours before bedtime, get a minimum of 10 minutes of aerobic exercise every day, identify and eliminate sleep stealers (like pets or electronics), and have a consistent and relaxing sleep environment that eliminates lights and disruptive noise.


            What’s preventing you from getting quality or adequate sleep? Sleep is an important part of maintaining a healthy lifestyle and metabolism. With these tools, you can improve your sleep cycles and circadian rhythms. If you have any thoughts or suggestions to improve sleep, please post them in the comments below.


Written by Anna Marie Oglesbee. B.S. in Nutritional Sciences from the University of Texas at Austin, ACE Certified Group Fitness Instructor, Certified Pharmacy Technician (CPhT).

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