We know that what you eat makes a difference to your health, but did you know that there's a growing body of evidence that when you eat matters too?
Let's start by talking about your circadian rhythm, which is your internal 'body clock'. This natural, internal process regulates the sleep-wake cycle and repeats roughly every 24 hours. It works thanks to a group of nerve cells in the brain which process light signals from the eyes and use this information to regulate key physiological processes. These include:
😴 Sleep-wake cycles: Your circadian rhythm helps regulate when you feel sleepy and when you wake up, ensuring you get adequate rest.
⚖️ Hormone production: Your circadian rhythm controls the release of hormones like cortisol and melatonin at the right times, helping you stay balanced.
🌡️ Body temperature: Your circadian rhythm helps regulate your body temperature throughout the day.
🍽️ Metabolism: Your circadian rhythm influences your metabolism, affecting how you digest food and use energy.
Scientists working in the field of chrononutrition are interested in finding out how your circadian rhythm interacts with food, metabolism and meal timing. Key research in this field includes:
⏰ Meal timing: Chrononutrition emphasizes the importance of aligning meal times with the body's natural rhythm to optimize digestion, nutrient absorption, and metabolism.
🥗 Nutrient distribution: Chrononutrition also considers the distribution of nutrients throughout the day. For example, consuming a higher proportion of carbohydrates earlier in the day and focusing on protein and healthy fats later in the day may be more in sync with the body's metabolic processes.
🏥 Impact on health: Research in chrononutrition has shown that the timing of food intake can affect various aspects of health, including weight management, blood sugar control, and cardiovascular health.
Now let's go a bit deeper, why does your eating window matter?
Well, eating windows of around 10 hours or less have been associated with several health benefits, according to some scientific studies. Including:
⚖️ Weight management:
Shorter eating windows have been shown to help with weight management by suppressing appetite, reducing overall calorie intake and promoting a more structured eating pattern. A 2021 publication ran a meta-analysis of randomized control trials in humans which showed that shorter eating windows (under 12h) with no enforced calorie restriction resulted in a significant decrease in weight, fat mass, and a slight decrease in total lean mass compared with the control (no time restrictions) diet. Eating late can have a negative impact on adipose tissue (that's your body's fat storage), which is highly sensitive to circadian patterns, by promoting fat storage. This is supported by several studies that report on how restricted eating windows can be protective of the negative health consequences of high-fat diets.
✨ Improved metabolic health:
Some randomized control trials in humans have indicated that time-restricted feeding can improve metabolic health. In particular, glucose tolerance, insulin sensitivity, and lipid profiles, that are essential factors for metabolic health.
🫀 Reduced risk of cardiovascular disease
Time-restricted eating has been shown to reduce markers of cardiovascular risks such as total cholesterol, HDL, LDL and blood pressure.
Some studies also point out that late-night eating (especially when close to bedtime) and skipping breakfast increase the risk of cardiovascular disease.
😴 Circadian rhythm alignment:
Eating within a shorter window can help align your eating habits with your body's natural circadian rhythms, which may lead to better sleep and overall health. This study and this review highlight the potential benefits of aligning eating patterns with circadian rhythms.
🦠 Gut microbiome:
There is some emerging evidence that suggests shorter eating windows could potentially modify and rejuvenate the gut microbiome. However, there is still a small amount of research in this area and is something we are very interested in at ZOE.
💛 ZOE science
In October 2022, ZOE launched the largest-ever community experiment into time-restricted eating or intermittent fasting (IF). It’s called The Big IF Study. The over 140,000 people who took part were asked to limit their eating window to under 10 hours, but they could start as early or late as they wanted. The Figure below shows some of the exciting learnings from the study. Check this page for more details.
Of course, as usual, nutrition is complex and not all studies are aligned on the effects that restricted eating times might have on health. Moreover, we know that each individual is different and will react to certain interventions in different ways, modulated by environmental factors, genetics etc. Always listen to your body and apply the health levers that are manageable for you in your day-to-day life to ensure you follow a healthy and sustainable approach. When making changes, be mindful of taking incremental steps 💛.
The interesting thing is that the relationship between food and your body clock is a two-way street. Your circadian rhythm influences how your body handles food at different times of the day, but changing how you eat also helps train your body clock (although to a lesser extent than light ☀️). Therefore, you can try to adjust meal times as well as your circadian rhythm to try and achieve your health goals.