New Spanish research has found that watching television appears to be the lifestyle factor most strongly associated with the risk of children being overweight or obese.

Led by the Barcelona Institute for Global Health (ISGlobal), a center supported by "la Caixa," the new study looked at data gathered from 1,480 Spanish children.

The researchers assessed five of the children's lifestyle habits, including physical activity, sleep time, television time, plant-based food consumption and ultra-processed food consumption, by asking parents to complete questionnaires on their child's habits at the age of 4. 

The researchers also measured the children's body mass index (BMI), waist circumference and blood pressure at four and seven years of age.

The findings, published in the journal Pediatric Obesity, showed that of the five behaviors analyzed in the study, television watching had the strongest association with overweight and obesity, with the children who were less active and spent more sedentary time in front of the television at the age of 4 more likely to be overweight, obese or have metabolic syndrome at age 7. 

However, when the researchers looked at the time spent being sedentary doing other activities, such as reading, drawing and doing puzzles, these activities did not appear to be associated with overweight or obesity.

"Most research to date has focused on the impact of individual lifestyle behaviors rather than cumulative effects," commented Martine Vrijheid, co-leader of the study. "However, it is well known that unhealthy behaviors tend to overlap and interrelate." Researcher Sílvia Fernández added that watching television "discourages physical activity and interrupts sleep time." The team also added that getting enough sleep in early childhood is essential for maintaining a healthy weight later in childhood. "Previous studies have shown that 45 percent of children are not sleeping the recommended number of hours per night," explained Fernández. "This is worrying because shorter sleep time tends to be associated with obesity."

The results also showed that high intake of ultra-processed foods at the age of 4, such as pastries, sweet beverages and refined-grain products, which are high in sugar, salt and saturated fat and low in nutritional value, was associated with a higher BMI at age 7.

Again, the researchers say television watching could also be impacting this lifestyle behavior. "When children watch television, they see a huge number of advertisements for unhealthy food," commented ISGlobal's Dora Romaguera, co-leader of the study. "This may encourage them to consume these products." 

The researchers concluded that setting healthy lifestyle habits during childhood, including limited television time, extracurricular physical activity, getting enough hours of sleep, eating lots of vegetables and avoiding ultra-processed foods, are important for good health during adulthood.