Summary: New research finds that people who prefer evenings—so-called night owls—face higher risks of cardiometabolic conditions such as type 2 diabetes and heart disease. One likely reason is that evening types tend to eat more irregularly and choose less healthy foods, often eating later into the night.
Source: Northumbria University.
Evening Chronotype Linked to Poorer Diet and Greater Cardiometabolic Risk
In the first international review of studies examining whether being an early riser or a night owl affects long-term health, researchers report mounting evidence that an evening chronotype is associated with a higher risk of chronic disease. The analysis, published in Advances in Nutrition, consolidates findings that link evening preference to less healthy eating patterns, poorer dietary choices, and increased incidence of conditions such as type 2 diabetes and heart disease.
Human physiology follows a roughly 24-hour cycle controlled by the internal biological clock, commonly called the circadian rhythm or chronotype. This clock influences many bodily processes, including appetite, sleep and wake cycles, and metabolic regulation. Chronotype varies between individuals, producing natural tendencies to fall asleep and wake earlier or later in the day.
The review highlights consistent patterns across multiple studies: people who prefer evenings generally consume more alcohol, sugary drinks, caffeinated beverages and fast food than morning types. Evening types often skip breakfast, eat later in the day, and show more irregular meal timing. Their diets typically contain fewer whole grains, less rye and fewer vegetables, and are characterized by fewer but larger eating occasions. In contrast, morning types tend to eat slightly more fruit and vegetables and maintain more regular meal schedules.
Eating late appears to be a key mechanism linking evening chronotype to metabolic disease. Glucose metabolism follows a circadian rhythm and usually declines across the day, reaching a low point at night. When people eat shortly before bedtime—as many night owls do—blood glucose remains elevated at a time when the body expects lower levels, which can impair metabolic processes. One study cited in the review found that evening types were 2.5 times more likely to have type 2 diabetes than morning types.
The review also underscores the effects of shift work, especially rotating shifts, which force repeated adjustments of the internal clock. These disruptions reduce insulin sensitivity and impair glucose tolerance, further increasing the risk of developing type 2 diabetes among shift workers.
The authors identified several additional trends related to chronotype, lifestyle and environment:
- Chronotype changes across the life course. Morning preference is more common in very young children, with more than 90% of two-year-olds showing an early preference. This shifts during childhood and especially during puberty, when many individuals develop a stronger evening preference that typically persists through adolescence and young adulthood. Around the early 50s, many people tend to revert toward a morning preference.
- Ethnicity, culture and living environment influence chronotype. Studies report variation between countries and between urban and rural areas within a country. For example, some populations show a higher prevalence of evening preference than others.
- Daylight exposure affects sleep timing. The review notes that more time spent outdoors is associated with advancing sleep timing (earlier sleep onset). Urban factors such as artificial light at night, noise and crowding can influence whether people lean toward morning or evening patterns.
- Evening types often accumulate sleep debt during the working week and then sleep longer on weekends to compensate. Morning types tend to have smaller weekday–weekend differences in sleep duration and timing.
The review was led by Dr. Suzana Almoosawi of Northumbria University and Dr. Leonidas Karagounis of Nestlé Health Science, with contributions from researchers at Nestlé Research, the University of Surrey, Örebro University, the National University of Singapore, the London School of Hygiene and Tropical Medicine, École Polytechnique Fédérale de Lausanne and Plymouth Marjon University.
Dr. Almoosawi explains that chronotype is shaped by genetic factors, sex and ethnicity, and that an evening chronotype in adulthood is associated with higher cardiometabolic risk—potentially driven by poorer dietary behaviors and irregular meal timing. The review also highlights gaps in knowledge about how chronotype affects food intake and metabolic risk across the lifespan, particularly in infants, children and older adults. While infants initially align their rhythms with caregivers, many children start to shift toward eveningness by age six, and the reasons for this change—whether biological, social or environmental—remain unclear.
Dr. Karagounis observes that existing cross-sectional evidence links evening preference to lower fruit and vegetable intake and higher consumption of energy drinks, alcohol, sugary and caffeinated beverages, along with higher intake of dietary fat. He and colleagues call for improved methods to measure chronotype and for longitudinal studies that follow chronotype, diet and cardiometabolic outcomes over time to better inform targeted public health strategies.
The authors recommend more population-based research that simultaneously measures chronotype, eating timing, frequency and regularity—collectively known as chrono-nutrition—and long-term health outcomes. Understanding how chronotype interacts with diet and metabolism could guide tailored interventions to prevent and manage chronic cardiometabolic disease.
Source: Northumbria University (Andrea Slowey).
Publisher: NeuroscienceNews reported the original press release.
Original research: “Chronotype: Implications for Epidemiologic Studies on Chrono-Nutrition and Cardiometabolic Health” by Suzana Almoosawi et al., published in Advances in Nutrition, November 30, 2018.
DOI: 10.1093/advances/nmy070
Abstract (summary)
Chrono-nutrition studies how timing, frequency and regularity of eating affect health. This narrative review examines evidence linking chronotype—an individual’s circadian preference—to dietary patterns and cardiometabolic outcomes. Research is limited for infants, children and older adults, and most available data in adolescents and adults are cross-sectional. The review identifies gaps in understanding how chronotype relates to the three chrono-nutrition dimensions and whether chronotype modifies diet–disease associations. The authors conclude that further longitudinal and population-based research is needed to clarify how chronotype, eating timing and dietary quality interact to influence cardiometabolic health.