With intermittent fasting and delayed breakfasts trending on social media, it can be tempting to skip your morning meal and head out the door, especially if you’re short on time and not feeling hungry. However, a new study published in the International Journal of Behavioural Nutrition and Physical Activity found that people with a lower BMI (body mass index) tended to follow two habits: fasting for longer overnight and eating breakfast early.

This new area of study is called chrononutrition and is gaining a lot interest amongst researchers. And while we are very good at understanding what to eat, new evidence is now explores the effects of when we eat and the impact it has on our health and weight.

The Study

Chrononutrition explores the relationship between meal timing and circadian rhythm on health. According to the study, meal timing patterns can disrupt the circadian system and affect metabolism. The researchers sought to study sex-specific chrono-nutritional patterns, assess their association with body mass index (BMI), and investigate the role of sleep in this relationship.

The Methods

The study included more than 7,000 participants aged between 40-65. Participants first answered questionnaires in 2018 about their weight and height, eating and lifestyle habits and socioeconomic status. Five years later in 2023, more than 3,000 participants returned. Their measurements were taken again along with new health questionnaires.

The researchers explored the association of the participants’:

• Time of first meal
• Number of eating occasions
• Nighttime fasting duration
• BMI
• Sleep duration and quality

Analysis was performed on these variables to identify chrono-nutritional patterns.

The Results

In the analysis, a later time of breakfast and more eating occasions were associated with a higher BMI. While longer nighttime fasting duration was associated with a lower BMI.

Luciana Pons-Muzzo, researcher at ISGlobal explained, ‘Our results, in line with other recent studies, suggest that extending the overnight fast could help maintain a healthy weight if accompanied by an early dinner and an early breakfast.

‘We think this may be because eating earlier in the day is more in line with circadian rhythms and allows for better calorie burning and appetite regulation, which can help maintain a healthy weight. However, it is too soon to draw definitive conclusions, so recommendations will have to wait for more robust evidence,’

The Conclusion

The researchers concluded that in the large group of participants, a later time of their first meal was associated with higher BMI. Longer nighttime fasting duration was associated with a lower BMI, both in cross-sectional and longitudinal analyses.

What Does This Mean for Us?

This study is one of many new pieces of research in the area of chrononutrition. In a recent review on chrononutrition, published in the Journal of Chronobiology, it explained that the light-dark cycles and timings of food intake teach our body’s internal clock — known as the circadian rhythm — to stay in sync. This coordination is essential for maintaining balanced sleep, digestion, and overall health.

Researcher at ISGlobal, Anna Palomar-Cros says, ‘Our research is part of an emerging field of research known as “chrononutrition”, which focuses not only on analysing what we eat, but also the times of day and the number of times we eat. At the basis of this research is the knowledge that unusual food intake patterns can conflict with the circadian system, the set of internal clocks that regulate the cycles of night and day and the physiological processes that must accompany them.’

Previous evidence has indicated that higher energy intake in the morning, particularly breakfasts higher in protein, could help regulate our appetite throughout the day. Along with the new evidence, we may be wise to focus on an early, high protein, energy dense breakfast and an early dinner for better appetite regulation over the day. However, as stated by the researcher, more studies are still needed to draw definitive conclusions at this point.