People who take siestas that are longer than 30 minutes are more likely to have a higher body mass index (BMI) and develop metabolic syndrome.
Siesta, which means “sixth hour” in Spanish, is an afternoon nap or rest usually taken during the hottest hours in Spain and other hot climate countries. A large 2021 study using the UK Biobank data associated siestas with an increased risk of obesity, but the link between afternoon nap duration and metabolic health is still poorly understood.
A new study led by investigators from Brigham and Women’s Hospital assessed 3,275 adults from the Spanish region of Murcia. Thirty-five percent of participants reported usually taking siestas. Of those, 16% had long siestas — 30 minutes or longer.
The study appearing in the journal Obesity found that people who took long siestas had a higher BMI and were more likely to have metabolic syndrome (MetS), a cluster of conditions that increases the risk of heart disease, stroke, and type 2 diabetes, compared to the non-siestas group. Moreover, those taking long siestas had higher fasting glucose levels, systolic and diastolic blood pressure, and waist circumference, which may indicate obesity.
In addition, the research associated long siestas with eating and going to bed later at night, consuming more calories during lunch, and smoking cigarettes, which may explain increased risks for obesity and MetS.
However, people who took short siestas under 30 minutes, also known as “power naps,” were less likely to have elevated systolic blood pressure than those without siestas.
The researchers note that it is possible that some factors may be a consequence of obesity and not siestas per se, and further research is necessary to determine whether a short siesta is more beneficial than a long one.
“If future studies further substantiate the advantages of shorter siestas, I think that that could be the driving force behind the uncovering of optimal nap durations and a cultural shift in recognition of the long-term health effects and productivity increases that can amount from this lifestyle behavior,” says co-author Frank Scheer, Ph.D., a senior neuroscientist and professor in the Medical Chronobiology Program in the Brigham’s Division of Sleep and Circadian Disorders.
Four in ten US adults have obesity, a condition associated with heart disease, stroke, type 2 diabetes, and certain types of cancer. Obesity rates are also climbing among children and adolescents, with nearly 20% of Americans ages 2 to 19 having obesity.
Factors such as eating patterns and physical activity levels may contribute to gaining excess weight. However, a 2022 report on the state of obesity in the United States emphasizes that the condition is caused by a combination of factors, such as societal, biological, genetic, and environmental, which are often beyond personal choice. For example, structural racism, poverty, and lack of access to quality healthcare are among key drivers of the differences in obesity rates across racial and ethnic groups.
While longer afternoon naps may contribute to developing obesity and metabolic syndrome, it is crucial to follow a balanced diet, exercise regularly, and undergo regular medical check-ups.