Recent research reveals that people who stay up late, known as night owls, are nearly 50% more likely to develop Type 2 diabetes compared to those who stick to an early bedtime.
Night owls typically have a “late chronotype,” meaning they prefer to go to bed and wake up later. This tendency has been associated with higher rates of tobacco use and unhealthy eating, which can lead to obesity and Type 2 diabetes.
“However, lifestyle alone does not fully explain the connection between a late chronotype and metabolic disorders,” explained Jeroen van der Velde, a researcher at Leiden University Medical Centre in the Netherlands. “While a late chronotype is linked to higher body mass index (BMI), we still need to understand how it affects body fat distribution.”
Van der Velde and his team investigated the relationship between sleep timing, diabetes, and body fat distribution using data from over 5,000 participants in the Netherlands Epidemiology of Obesity study. Most participants were in their mid-50s and provided information about their typical wakeup and bedtime.
Participants were classified into three groups: early chronotype (20% with the earliest bedtimes), late chronotype (20% with the latest bedtimes), and intermediate chronotype (60% with mid-range bedtimes). The study tracked these individuals for nearly seven years, during which 225 developed Type 2 diabetes.
After accounting for factors such as age, sex, education, body fat, physical activity, diet, and alcohol consumption, the researchers found that late chronotypes had a 46% higher risk of diabetes compared to those with an intermediate chronotype. This suggests that the increased risk cannot be solely attributed to lifestyle choices.
Van der Velde proposed that the mismatch between a late chronotype’s internal body clock and societal schedules might contribute to this risk. This “circadian misalignment” could disrupt metabolism and lead to Type 2 diabetes.
Interestingly, early chronotypes, who were expected to have a similar risk to intermediate chronotypes, actually showed a slightly higher risk, though this finding was not statistically significant.
The study also noted that late chronotypes had higher BMIs, larger waist circumferences, more visceral fat (fat around internal organs), and higher liver fat compared to intermediate chronotypes.
“Late chronotypes seem to face a greater risk of Type 2 diabetes, potentially due to increased body fat, including visceral and liver fat,” Van der Velde said. “Future research should explore whether adjusting lifestyle habits could improve metabolic health for late chronotypes.”
Van der Velde suggested that night owls might benefit from setting a specific time to stop eating, such as 6 p.m., as meal timing can influence digestion and metabolism. “Although the evidence is not yet definitive, we aim to provide specific advice on lifestyle timing in the future,” he added.
These findings will be presented this week at the annual meeting of the European Association for the Study of Diabetes. They follow recent studies suggesting that being a night owl may benefit cognitive function but negatively impact mental health.
Dr. Mitchell Roslin, chief of bariatric and metabolic surgery at Northern Westchester Hospital and Lenox Hill Hospital, noted that poor sleep habits contribute to obesity and diabetes by increasing stress hormones like cortisol. “Cortisol and stress further raise glucose levels and promote weight gain, which can lead to sleep apnea and insulin resistance,” Roslin said. “This creates a downward spiral.”
