Sept. 15, 2023 -- Our internal body clock, or circadian rhythm, helps us feel alert during the day and tired at night. But travel, shift work, caring for a newborn, or anything that messes with your sleep schedule can throw that delicate system off-kilter.
In the short term, this can lead to fatigue, insomnia, or an upset stomach. But evidence suggests that over time the effects can be more serious, increasing health risks like cardiovascular disease, diabetes, depression, and cancer.
Experts often recommend light exposure to ease the effects, but research has been finding that meal timing may be just as important. A study published this month in Chaos suggests that eating a large meal in the early morning could be key.
"Both our study and experimental evidence suggests that keeping [light and feeding] cues in sync -- such as avoiding eating at night -- is beneficial,” said lead study author Yitong Huang, PhD, a researcher in the department of molecular biosciences at Northwestern University.
What the Researchers Did
A lot of research on circadian rhythm has focused on the “central” body clock, found in part of the brain called the suprachiasmatic nucleus. The central clock responds to sunlight. But research over the past 20 years has revealed that the circadian system involves not just one body clock but many. Present in almost every cell and tissue, these clocks calibrate to different cues, said Huang. Many organs reset with meals.
The researchers developed a theoretical mathematical model that allowed them to take a new approach – studying how these clocks interact, not just with external cues, but also with each other.
“Our study considers two populations of clocks,” said Huang – one that responds to light (the brain), and another that responds to food (the liver).
In the study, the researchers ran simulations of a traveler going from New York to Paris (a 6-hour time difference).
- Failing to adjust mealtimes to the new time zone resulted in a 9-day jetlag recovery.
- Spacing three meals throughout the light hours reduced recovery time to 6 days.
- Doubling the size of breakfast and skipping dinner for the first three days sped recovery even more, to 5 days.
The researchers concluded that a large meal in the early morning helps the body’s clocks align, combating the effects of jet lag.
“Eating at night activates the liver clock at a time when the [brain] clock wants to rest,” the researchers write in the study.
The Case for a Big Breakfast
The findings build on growing evidence that eating more in the morning than in the evening is good for us. In addition to kickstarting our body clock, it may help lower body weight and improve blood sugar, research shows.
Psychiatrist Alex Dimitriu, MD, founder of Menlo Park Psychiatry and Sleep Medicine in Menlo Park, CA, who was not involved the study, points to previous research in mice.
"Mice are normally nocturnal creatures, and some studies have found that they will switch to being awake during the day if that's when food is available," Dimitriu said. "In mice, food-seeking behavior drives wakefulness, and this recent study suggests the same may be true for humans."
This also aligns with advice from sleep experts to avoid big meals before bed, said Dimitriu, who’s noticed that his patients sleep best if they limit food after sunset and eat a regular breakfast.
Just how big should breakfast be? More research would be needed to link the study’s model to specific calorie counts for humans, Huang said. But you can think about it in relative terms: Simply front-load your daily calories so you’re getting more earlier in the day and fewer at night.
The researchers plan to run more experiments using their math model. Ultimately, its predictions could lead to new interventions or even an app that recommends optimal mealtimes, Huang said.
"Because food schedules are often easier to adjust,” Huang said, “we believe that this model paves the way for more personalized intervention strategies.”
