In the hustle and bustle of modern lives, the best weight-loss tips are simple ideas that will hopefully stick, and recent research has revealed a couple of new ones that qualify: fast for longer overnight, and eat breakfast earlier.
Researchers led by a team from the Barcelona Institute for Global Health (ISGlobal) in Spain analyzed diet and weight data from 7,074 individuals aged 40 to 65, finding that early breakfast and early dinner with no eating in between were associated with lower body mass index (BMI) scores after five years.
Although BMI is a problematic measure of obesity, the findings add to a growing pile of research looking at how the times we eat can affect our health.
Here, the researchers believe their findings may be linked to the body's circadian rhythms, those internal biological clocks we all have that run on a 24-hour cycle and deliver bodily cues about when to rest and when to wake.
"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," says epidemiologist Luciana Pons-Muzzo of ISGlobal.
"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."
The researchers used several statistical methods, adjusting for variables such as age and sleep, and found that later breakfast timing and more frequent eating were associated with higher BMI, whereas longer overnight fasting was associated with lower BMI.
"These associations were particularly evident in premenopausal women," the researchers write.
The team also conducted a cluster analysis to group participants based on their eating habits. This helped clarify the study's main findings and allowed the researchers to separate participants by sex.
One of the groupings was observed exclusively in men: Individuals in this category ate their first meal after 2 pm, fasted overnight for 17 hours on average, and were more likely to drink, smoke, and be unemployed.
"What we observed in a subgroup of men who do intermittent fasting by skipping breakfast is that this practice has no effect on body weight," says epidemiologist Camille Lassale of ISGlobal.
"Other intervention studies in participants with obesity have shown that this tactic is no more effective than reducing calorie intake in reducing body weight in the long term."
The study isn't structured in a way that can prove direct cause and effect, but there are some significant associations here. If you're currently skipping breakfast to try to cut down on calories, you might be better off shifting your dinner time earlier and eating breakfast instead.
"There are different ways of practicing what is known as 'intermittent fasting,' and our study relates to one of them, which is overnight fasting," Lassale says.
Some of the internal timings that a long overnight fast and an early breakfast might sync better with relate to regulating insulin production and managing fat storage, the researchers suggest – though further study will be needed to know for sure.
Sleep might also play a role here. We know getting enough shut-eye is crucial for our health, and the eating patterns highlighted here may be most conducive to that.
Future research could track larger, more diverse groups of people over a longer period and test interventions in clinical trials by giving participants specific instructions about eating times and checking what changes.
Related: The Secret to Healthy Eating Might Not Be What You Eat – But Something Else
"Our research is part of an emerging field of research known as chrononutrition, which focuses not only on analyzing what we eat, but also the times of day and the number of times we eat," says epidemiologist Anna Palomar-Cros of ISGlobal.
"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."
The research has been published in the International Journal of Behavioral Nutrition and Physical Activity.