Have you heard of the "circadian rhythm"? Did you know it is very important for your diet and affects whether you manage to see the desired results? Read below for more information.

What is the circadian rhythm?
The word "circadian" comes from the Latin circa (around) and diem (day) and refers to a daily cycle of approximately 24 hours. Studies from the 18th century conducted on plants provided the first evidence of the existence of internal biological oscillators that internally monitor the Earth's rotation and lead to these 24-hour periodic phenomena in organisms.

The "circadian clocks" are influenced by light and synchronize the processes of energy collection and utilization according to sunrise and sunset. In humans, the endogenous circadian system is located in the suprachiasmatic nucleus of the hypothalamus in the brain, and the sleep hormone melatonin is secreted by the pineal gland, which is also in the brain.

In simple terms, humans have an "installed system" inside them that helps synchronize the various processes occurring in their bodies with nature. Circadian rhythms regulate various bodily functions, including hormone secretion, internal body temperature, autonomic nervous system activity, cognitive functioning and efficiency, and the response to food.

What affects our circadian rhythm?
The circadian rhythm can be influenced by various external factors, such as environmental (e.g., temperature), behavioral (e.g., meal schedule, exercise, diet), professional (e.g., work schedule, night shifts), social (e.g., daily activities, family situation), biological (e.g., age, biochemical factors), and pharmaceutical (e.g., sleep medications).

If the function of the circadian clock is disrupted, it is likely that problems may arise in various bodily functions.

How can diet regulate or disrupt our "internal clock"?
Diet has been shown to influence our circadian rhythm and vice versa. Firstly, our body is programmed to process food better in the morning. This happens because it regulates the hormones that control blood glucose levels. Meanwhile, nutrients, including macro- and micronutrients and natural bioactive compounds, can directly or indirectly regulate the circadian rhythm.

What should I watch out for so that my diet aligns with my circadian rhythm?
Research on these issues has not yet concluded whether there are basic rules that all people must follow without exception. For example, it is not clear whether everyone should try waking up early, eating breakfast, and having a very light dinner. There is the theory of the "early" and "late" chronotype, according to which the former is, let’s say, the "morning type" who does everything better in the morning, and the latter is the "evening type" who wakes up later, sleeps later, and functions better at night.

So, regardless of this issue, I think some basic points that everyone without exception should pay attention to are the following:

• Have good, quality, restful sleep every night, lasting 6–8 hours, neither more nor less. To improve your sleep, learn about Sleep Hygiene and study how diet can help improve sleep.
• Eat breakfast. From my experience, 99% of people need a quality breakfast.
• Do not start intermittent fasting without supervision. Please, start intermittent fasting only with the approval of your doctor and Dietitian-Nutritionist, as it is not suitable for everyone and requires finding the right plan for you.
• Distribute the carbohydrates you eat throughout the day wisely. If you think carbohydrates only concern people with diabetes, you’re mistaken. As we said, our body handles carbohydrates better earlier in the day, so don’t load your dinner with too many carbohydrates, such as a large portion of pasta or pizza. Also, choose carbohydrates with a low glycemic index.
• Try to reduce screen time, as blue light hinders melatonin production. Try other hobbies, especially in the evening, such as walking, reading a book, going out, or playing board games with loved ones.
• Increase your exposure to natural sunlight during the day. Make sure to get at least 20–30 minutes of sunlight in the morning so that your body recognizes the start of the day.
• Choose intense exercise—especially in the morning—and leave more relaxed forms of activity for the evening. The body can respond better to morning workouts.
• Ensure your midday nap is short, about 20–30 minutes, and take it earlier in the day (for example, before 5–6 PM).
• People who suffer from jet lag due to travel need to adapt gradually to the new time zone.
• People who work night shifts need to adjust their meal times appropriately and create complete darkness during their sleep hours by using heavy curtains or a sleep mask.

Source
Adapted from Magdalinou Aikaterini, “Investigation of the relationship between breakfast, sleep quality, and glycemic regulation in patients with type 2 diabetes” [Master’s thesis]. Athens: National and Kapodistrian University of Athens, Medical School, MSc "Diabetes Mellitus and Obesity"; 2024.