A new study suggests that staying up late and being a "night owl" may be linked to poorer metabolic health and higher body fat.
The study followed healthy women in Auckland, New Zealand, and looked at whether their sleep pattern, known as chronotype, is linked to eating habits, body fat, and overall metabolic health.
For this study, researchers included 287 women aged 18 to 45, including 130 New Zealand Pacific women and 157 New Zealand European women.
They used the Munich Chronotype Questionnaire (MCTQ) to classify participants as morning, intermediate, or evening types based on their sleep patterns.
Women who usually slept from 11pm to 8am were considered intermediate types.
Participants recorded everything they ate and drank over five non-consecutive days, including three weekdays and two weekend days.
Instead of relying only on BMI, the researchers used DXA scans to measure body fat and where it was stored, such as around the waist and hips.
They also tested blood samples to measure blood sugar, cholesterol, triglycerides, insulin and hormones linked to appetite and body fat.
Unhealthy pattern
Researchers found that women who were night owls ate fewer healthy, nutrient-rich foods than those who preferred waking up early.
They also tended to eat more of their daily calories in the evening, which was linked to a higher body fat percentage and a greater risk of obesity.
They further noted that, as night owls usually ate very little in the morning and consumed most of their food late at night, they had a higher body mass index (BMI) and more body fat than morning people.
In the findings, published in Frontiers in Nutrition, blood tests showed that night owls had higher insulin and triglyceride levels and lower levels of "good" HDL cholesterol.
They also had higher levels of leptin, a hormone linked to body fat, and lower levels of ghrelin, the hormone that signals hunger.
Moreover, compared with morning and intermediate types, night owls had poorer results for almost every health measure.
They had higher BMI, more body fat, and more fat stored around the waist, which is linked to a greater risk of health problems.
They also ate less fibre and consumed fewer essential vitamins and minerals.
Overall, the researchers found that even though women in all three groups consumed similar amounts of calories and nutrients, those who stayed up late had poorer metabolic health, higher body fat, and lower-quality diets. – dpa
