Going to sleep at different times throughout the week could be wreaking havoc on our health, a study has suggested.

The finding is a result of the ZOE project by King’s College London, which saw scientists study people who usually got at least seven hours of sleep a night. After measuring gut samples and the glucose levels of participants, they found that people who went to bed and woke up 90 minutes later at weekends had gut bacteria linked to heart attacks, strokes and obesity.

While some of the findings were linked to diet, the data indicates “other as yet unknown factors may be involved,” according to Dr Wendy Hall, from King’s College, who emphasised the impact sleep can have on our health.

The expert explained: “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.”

Kate Bermingham, of King’s College, added: “Sleep is a key pillar of health. Even a 90-minute difference can encourage microbiota species which have unfavourable associations with your health.”

In particular, three out of the six types of gut bacteria more common in the group who favoured weekly lie-ins are known to be linked to poor health. Those who went to sleep and woke up at very different times – which is known as having social jetlag – were also more likely to consume more chips, crisps, and sugary drinks, but less fruit.

“Poor quality sleep impacts choices – and people crave higher carb or sugary foods,” noted Dr Bermingham.

Following the study, published in the European Journal of Nutrition, Dr Hall said intervention trials are needed to “find out whether improving sleep time consistency can lead to beneficial changes in the gut microbiome and related health outcomes.”