Getting seven hours and 18 minutes sleep a night might be the “sweet spot” for staying healthy and avoiding diabetes, a study has found.

Researchers said poor and inconsistent sleep could create a “vicious cycle” and that overindulging in long weekend lie-ins causes just as much damage as insomnia.

A team at Nantong University in China examined data from 23,000 adults in the US, who recorded their nightly sleep and had their blood sugar levels measured.

There was a U-shaped curve between the hours of sleep each night and blood sugar control, with 7 hours and 18 minutes each night found to be the “sweet spot”.

Having an extra two hours of sleep at the weekend to catch up was associated with worse outcomes. The authors concluded that weekend catch-up sleep was “beneficial only in moderation and specifically for those with weekday sleep debt, whereas it may be detrimental for those who already sleep sufficiently”.

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The study used a measure called estimated glucose disposal rate, which indicates insulin resistance — a condition in which the body does not respond to insulin well, meaning blood sugar is high. Insulin resistance is the precursor to type 2 diabetes, a condition which affects four million in the UK and usually develops because of obesity.

The research was published in the journal BMJ Open Diabetes Research & Care. People involved in the study reported an average of seven and a half hours of sleep in the week, and half of them said that they also had catch-up sleep at the weekend. Keeping a consistent sleep schedule of seven to eight hours a night was associated with healthy blood sugar levels.

Research shows that a lack of sleep increases inflammation, blood pressure and stress hormones, which can contribute to chronic conditions including heart disease and type 2 diabetes.

The study said that having poor blood sugar control can also lead to poor sleep, adding: “This creates a potential vicious cycle wherein metabolic dysregulation disrupts normal sleep patterns, and the resultant abnormal sleep (including extended duration) further aggravates metabolic health.”

Dr Lucy Chambers, head of research impact and communications at Diabetes UK, said: “Type 2 diabetes doesn’t have a single cause. Genetics, age and body weight are well‑known contributors among many, but sleep is often an under‑recognised factor.

“This research adds to evidence linking sleep patterns with type 2 diabetes risk, and is a reminder that nutrition, physical activity and sleep are all essential pillars of good health.”

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Professor Naveed Sattar, of the University of Glasgow, said: “There is plenty of evidence showing that shorter sleep — typically less than seven hours a night — is linked with a higher risk of developing type 2 diabetes. Poor sleep disrupts appetites, meaning people often eat more after a poor night’s sleep, and simply being awake for longer creates more opportunities to eat. In addition, inadequate sleep may directly affect key hormones, including stress hormones, that influence glucose levels.

“The current study adds to this body of research, although it is observational, so we must interpret the findings with some caution. That said, genetic studies also suggest that people predisposed to shorter sleep are at higher risk of future diabetes, strengthening the likelihood of a causal link.

“The practical message is that people should work hard at developing a good sleep hygiene: going to bed at consistent times, creating a wind‑down routine, and reducing screen use — particularly mobile phones — in the hour before bed. The easy access to digital distractions is likely contributing to declining sleep quality and duration, which may in turn contribute to more obesity and diabetes.”