Researchers have suggested that although reaching for a snack before bed may seem harmless enough, this could be putting your liver health at risk, adding to growing evidence that meal timing may matter – in addition to what and how much you eat – reports Everyday Health.
In a study of nearly 200 000 adults, those who reported eating late at night had a nearly 40% higher risk of metabolic dysfunction-associated steatotic liver disease (MASLD), previously called fatty liver disease, than their peers who didn’t eat late.
They also had a nearly 30% higher risk of cirrhosis, or severe liver scarring.
“We know the liver is very much in tune with the body’s circadian rhythms,” said Robert Wilechansky, MD, a study co-author and a hepatologist at Oregon Health and Science University in Portland.
“So we’re interested in changing the timing of eating in a way that could make a difference in health without changing the composition of what people eat.”
The findings were published in Clinical Gastroenterology & Hepatology.
The researchers analysed data from more than 199 000 participants in three long-running US research projects: the Nurses’ Health Study, the Nurses’ Health Study II, and the Health Professionals Follow-up Study.
These are some of the longest-running cohort (or group) studies ever undertaken, aimed at tracking how diet and lifestyle affect long-term health and disease risk.
For this study, researchers divided participants into two groups: those who reported late-night eating (after dinner or before bed) and those who didn’t. Then they compared rates of MASLD and cirrhosis between the groups.
Over an average follow-up period of 16 years, about 4 500 participants developed MASLD, and 315 developed cirrhosis. Late-night eaters were 36% more likely to develop MASLD, and 28% more likely to develop cirrhosis than their peers who didn’t eat later in the evening.
Researchers found that the link between late-night eating and liver disease remained even after accounting for factors such as body mass index (BMI), diabetes, physical activity, alcohol consumption, total calories and diet quality.
For Bernard Srour, PharmD, PhD, a research professor at the French Institute for Agriculture, Environment and Food (INRAE) in Paris, the long follow-up period is particularly noteworthy.
“Knowledge is scarce on the long-term associations between meal timing and MASLD,” he said, noting that much of the existing evidence comes from animal studies or short-term clinical trials. Srour was not involved in the new research.
MASLD, previously known as non-alcoholic fatty liver disease, occurs when excess fat builds up in the liver in people with metabolic risk factors like obesity or type 2 diabetes. Some people with MASLD develop inflammation and liver damage that can eventually lead to cirrhosis.
One possible explanation involves the body’s circadian rhythms, the internal biological clocks regulating functions such as sleep, digestion, and metabolism throughout the day.
The liver has its own internal clock, which helps co-ordinate how it processes and stores nutrients. “Meal timing is known to be the main external time-cue for peripheral clocks of the liver,” Srour says.
In other words, eating at a time when the body is biologically preparing for sleep could interfere with those processes.
“We are seeing over and over again that the timing of behaviours, whether it’s sleep, eating, or exercise, really matters,” said Andrew McHill, PhD, a co-author of the study and an associate professor and sleep and circadian physiologist at Oregon Health and Science University.
McHill said the liver may be particularly vulnerable when eating patterns fall out of sync with the body’s circadian rhythms.
In addition, insulin sensitivity – or how effectively the body responds to the hormone insulin – also generally decreases at night.
“Based on this, taking in calories at a time when the liver metabolism is working less efficiently may be part of the reason for this association,” Wilechansky said.
Limitations, areas of future research
Despite its size and lengthy follow-up period, the study was observational, meaning researchers couldn’t determine whether late-night eating directly contributed to liver disease.
“Even though we were able to adjust for a number of factors (like diet quality, BMI, diabetes, and physical activity), this type of observational analysis is not able to account for all possible factors that could influence the result,” Wilechansky said. “It also is not able to prove causation, only that there is a correlation or association.”
The researchers also relied on self-reported eating habits and liver disease diagnoses. Srour said this could be particularly problematic for MASLD, as many people with the condition don’t know they have it, because of a lack of noticeable symptoms.
Another limitation is that researchers couldn’t determine exactly what time participants ate, how much they consumed at night, or how close their meals were to bedtime. Srour said this distinction could make a difference, as eating a small snack after an early dinner may not have the same impact as consuming a large, rich meal shortly before sleep.
In addition, because participants were predominantly white healthcare professionals, the findings may not be generalisable to broader populations.
Should you avoid eating before bed?
So, how late is too late to eat? Researchers don’t yet have a definitive answer. “While we don’t yet know the exact timing of when to stop eating, and it is very likely person-dependent, we generally think you should stop at least two to four hours before your habitual bedtime,” McHill said.
That recommendation wasn’t tested in the study, though. “It is way too soon to give precise recommendations,” Srour added. In the meantime, experts say the findings suggest that meal timing deserves more attention – but there's no reason to panic about the occasional late-night snack.
Everyday Health article – Snacking before bed may increase liver disease risk (Open access)
See more from MedicalBrief archives:
MASLD cases on the increase – Lancet British study
MASLD to affect almost 2bn people by 2050 – Lancet
How later mealtimes may be linked to earlier death – UK study
MAFLD: A new name and definition bringing hope for patients with fatty liver disease