Taking long siestas was tied to obesity risk, especially in smokers or people who ate late, large lunches, in a middle-aged, healthy population in Spain.
This was a cross-sectional study in 3275 healthy adults aged 18-65 living in Spain — where it is common to take a midday nap (siesta) — recruited from weight-loss clinics into the Obesity, Nutrigenetics, Timing, and Mediterranean (ONTIME) study.
Participants were a mean age of 40 years, 78% were women, and 87% had overweight or obesity. Mean body mass index (BMI) was 31 kg/m2.
They replied to questionnaires about lifestyle, including how often they took long (> 30 minutes) or short (≤ 30 minutes) siestas.
35% of participants were habitual nappers and the average number of naps taken was four naps per week. These rates were similar to other countries in Europe, America, and Asia, where taking siestas is culturally embedded.
16% usually took long siestas and 20% took short siestas for an overall average of about 43 minutes on weekdays or weekends, mainly for relaxing (49%) or tiredness (36%).
Compared with participants who skipped siestas, those who usually took long midday naps had a 21% higher BMI, a higher waist circumference, higher fasting blood glucose, and higher blood pressure; they also had a 41% increased odds of metabolic syndrome (P = .015) and a 23% increased odds of obesity (although this was only a trend, P = .051).
In contrast, compared with not taking a siesta, regularly taking a short nap was associated with a 21% lower odds of having elevated systolic blood pressure (≥ 120 mmHg; P = .044).
Smoking (more cigarettes/day), later meals, later nighttime sleep, and eating a large lunch before the siesta partly explained the association between long siestas and higher BMI.
“These results call for studies to investigate whether short siestas are advisable over long siestas, especially in those individuals who usually have delays in eating and sleeping schedules, or in those who smoke,” say the authors in their report.
The authors, from the University of Murcia, Spain, the University of Guadalajara, Mexico, and Brigham and Women’s Hospital, Boston, Massachusetts, published their findings in Obesity.
This was a cross-sectional observational study, and so it cannot show that napping causes obesity. Napping was self-reported, so there may have been recall bias. Participants may have had undiagnosed sleep disorders.
The study received no commercial funding. The authors have reported no relevant financial disclosures.
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