“New research, to be presented at the Annual Meeting of the European Association for the Study of Diabetes (EASD) in Madrid, Spain (9-13 September), has found that night owls have a higher BMI, larger waists, more hidden body fat, and are almost 50% more likely to develop type 2 diabetes (T2D) than those who go to bed earlier.”

“The lead researcher, Dr. Jeroen van der Velde, from Leiden University Medical Centre in the Netherlands, stated that previous studies have shown that individuals with a late chronotype – meaning they prefer to go to bed late and wake up later – tend to have unhealthy lifestyles. People with late chronotypes are more likely to smoke or have an unhealthy diet, which may explain why they are at a higher risk of obesity and metabolic disorders, including type 2 diabetes.”

“We believe that lifestyle alone cannot entirely account for the link between a late chronotype and metabolic disorders. Furthermore, although it is established that a late chronotype is linked to higher BMI, the extent to which chronotype influences body fat distribution remains unclear.”

In order to learn more, Dr. van der Velde and colleagues conducted a study on over 5,000 individuals as part of the ongoing Netherlands Epidemiology of Obesity study. They looked into the connection between sleep timing, Type 2 Diabetes (T2D), and body fat distribution to understand how body fat influences disease.

The analysis included participants, 54% of whom were female, with an average age of 56 years and an average BMI of 30 kg/m2.

Participants completed a questionnaire about their typical bedtime and waking times, from which the midpoint of sleep (MPS) was calculated.

The participants were then divided into three groups: early chronotype (the 20% of participants with the earliest MPS), late chronotype (the 20% of participants with the latest MPS), and intermediate chronotype (the remaining 60% of participants).

Waist circumference and BMI were measured for all participants. MRI scans and MR spectroscopy were used to measure visceral and liver fat in 1,526 participants.

The participants were followed up for a median of 6.6 years, during which 225 were diagnosed with T2D.

Here is the revised text:”The results, which were adjusted for age, sex, education, total body fat, and a range of lifestyle factors (physical activity, diet quality, alcohol intake, smoking, and sleep quality and duration), showed that compared with an intermediate chronotype, participants with a late chronotype had a 46% higher risk of T2D.”

This suggests that the increased risk of type 2 diabetes in late risers cannot be solely attributed to lifestyle factors.

“We believe that other mechanisms are also at play,” says Dr. van der Velde. “A likely explanation is that the circadian rhythm or body clock in late chronotypes is out of sync with the work and social schedules followed by society. This misalignment can lead to metabolic disturbances and ultimately, type 2 diabetes.”

The team also looked at T2D risk in early chronotypes. 

“We expected early chronotypes to have a similar risk of developing type 2 diabetes as intermediate chronotypes,” said Dr. van der Velde. “Our results showed a slightly higher risk, but it was not statistically significant.”

The results also indicated that individuals with a late chronotype had a 0.7 kg/m2 higher BMI, a 1.9 cm larger waist circumference, 7 cm2 more visceral fat, and 14% higher liver fat content, in comparison to those with an intermediate chronotype.

Dr. van der Velde concludes, “Individuals with a late chronotype seem to have a higher risk of developing type 2 diabetes compared to those with an intermediate chronotype. This may be due to higher levels of body fat, including increased visceral and liver fat.”

“The next step is to study if individuals with a late chronotype experience improvements in metabolic health when they adjust the timing of their lifestyle habits.”

“We are currently part of the TIMED consortium, which is examining the complex interplay of the timing of sleep, food intake, and physical activity in relation to type 2 diabetes. Our previous research has demonstrated the importance of the timing of physical activity in relation to insulin resistance.”

“If you have a tendency to stay up late, you may be more inclined to eat later in the evening,” says Dr. van der Velde. “Although our study didn’t directly measure this, there is increasing evidence that limiting the times when you eat, for example, not eating anything after a certain time like 6 pm, could have metabolic benefits.”

“Night owls concerned about the increased risk of type 2 diabetes may want to avoid eating late in the evening, at least.”

“The evidence isn’t there yet, but we aim to provide specific advice on the timing of lifestyle behavior in the future.”