Those who use an alarm clock during the week but have a lie-in at weekends eat less healthily. Photo / 123RF
Small inconsistencies in sleeping patterns have been found to make a significant difference to overall health.
Having a weekend lie-in of just 90 minutes could be enough to wreck your diet, research suggests.
Small inconsistencies in sleeping patterns were found to make a significant difference to gut health, which can increase the risk of diabetes, heart disease and obesity.
Those who used an alarm clock during the week, but stayed up later and let themselves have a lie-in at weekends ate less healthily, with more sugary drinks and lower intake of fruit and nuts.
They were also found to have higher markers of inflammation - a sign of poorer health, with major differences in their gut microbiome, compared with those with consistent sleeping patterns.
A wealth of research has previously shown that shift workers have worse health, with night work affecting circadian rhythms.
But the study of almost 1,000 people by King’s College London and the nutrition company ZOE is the first of its kind to show that even small changes in sleep patterns could make a major difference.
While some of the changes are likely to be explained by the fact those without consistent sleep habits might be more likely to choose unhealthy fare, experts said the findings suggest that disrupting the body clock may itself negatively impact gut health, increasing the risk of diseases.
Researchers said the study was the first to find multiple associations between “social jet lag” - the shift in the internal body clock when sleeping patterns change between workdays and free days - and diet quality, habits, inflammation and gut microbiome composition in a single cohort.
The study, published in The European Journal of Nutrition, found 17 bacterial species where levels were significantly different depending on whether participants had consistent or inconsistent sleep patterns.
Nine were more common in those with “social jet lag”, with eight more frequently seen in those who kept regular bedtimes.
Three of the species that were more abundant among those who liked lie-ins have unfavourable associations with health, with links to obesity, cardiometabolic health and higher levels of inflammation and risk.
Dr Wendy Hall, of King’s College London and the senior author of the study, said: “We know that major disruptions in sleep, such as shift work, can have a profound impact on your health.
“This is the first study to show that even small differences in sleep timings across the week seems to be linked to differences in gut bacterial species. Some of these associations were linked to dietary differences but our data also indicates that other, as yet unknown, factors may be involved.
“We need intervention trials to find out whether improving sleep time consistency can lead to beneficial changes in the gut microbiome and related health outcomes.”
The composition of the microbes in the gut (microbiome) can negatively or positively affect health by producing toxins or beneficial metabolites.
Specific species of microbes can correspond to an individual’s risk of long-term health conditions such as diabetes, heart disease and obesity.
Researchers found that just a 90-minute difference in the timing of the midpoint of sleep - the halfway point between sleep time and wake-up time - is associated with differences in gut microbiome composition.
This kind of difference could be seen in a person who went to bed at 11pm at night in the week, to rise at 6am, but stayed up till 12.30am at the weekend, and woke at 7.30am.
First author Kate Bermingham, PhD, of King’s College London and senior nutrition scientist at ZOE, said: “Sleep is a key pillar of health, and this research is particularly timely given the growing interest in circadian rhythms and the gut microbiome. Even a 90-minute difference in the mid-point of sleep can encourage microbiota species which have unfavourable associations with your health.”
Dr Sarah Berry, of King’s College London and chief scientist at ZOE, added: “Maintaining regular sleep patterns, so when we go to bed and when we wake each day, is an easily adjustable lifestyle behaviour we can all do, that may impact your health via your gut microbiome for the better.”
While previous studies into the association between social jet lag and metabolic risk factors have been done in populations with obesity or diabetes, this cohort consisted of mainly lean and healthy individuals with most getting more than seven hours sleep throughout the week.
In the cohort of 934 people from the ZOE PREDICT study, the largest ongoing nutritional study of its kind, researchers assessed blood, stool and gut microbiome samples as well as glucose measurements in those whose sleep was irregular compared with those who had a routine sleep schedule.