One in five children is overweight

According to new research, skipping breakfast or excessive screen time are risk factors for developing obesity

Uno de cada cinco menores tiene exceso de peso
Two children playing a video game.jopstock (Getty Images)
Jessica Mouzo

Excess weight is one of the top global health problems that plague the world. Obesity is already the most common form of malnutrition in most countries, and its incidence continues to rise throughout the globe. A scientific review from the University of Sichuan (China) published on Monday in the journal Jama Pediatrics highlights the impact of this phenomenon on children and adolescents. In line with other previous research, it confirms the problem is on an upward trend: the number of cases recorded between 2012 and 2023 is 60% higher than the number reported in the first decade of this century. According to the study, one in five children on the planet is now overweight or obese.

The researchers identified great heterogeneity in the prevalence between countries and also diverse risk factors, from dietary to behavioral. For example, skipping breakfast, excessive screen time, and having a mother who smoked during pregnancy increase the likelihood of childhood obesity. Scientists also warn that excessive fat accumulation in the first years of life can continue into adulthood and is the gateway to other diseases, such as depression and hypertension.

This is not the first time that attempts have been made to put numbers and perspective on this phenomenon. Seven years ago, research estimated that 107.7 million children (5% of the global child population) and 603.7 million adults were obese in 2015. Even back then, the trend was on the rise, and time has confirmed its upward trajectory. According to estimates by the World Obesity Federation, 310 million people aged from five to 19 will have the disease by 2025; a number that will rise to 350 million in 2030. The new research published in Jama Pediatrics supports this trend, and delves into the risk patterns and dangers of the disease.

Scientists at Sichuan University reviewed more than 2,000 studies from 154 countries involving nearly 46 million people. The research concluded that the global prevalence of obesity in children and adolescents is 8.5%, although there is great variability between regions. For example, in Vanuatu, an island in Oceania, the prevalence is 0.4% and in Puerto Rico, 28.4%. In Spain, it is 9.28%.

To begin with, high-income countries have higher rates of excess weight, but large differences were also identified between these nations: in the United States, the prevalence is 18.6% and in Japan, it is close to 4%. “European countries and the U.S. often embrace a diet preference of processed food, which are typically abundant in unhealthy fats, added sugars, and refined carbohydrates. In contrast, diets rich in whole grains and vegetables, which are generally regarded as healthier options, have historically been prioritized in Southeast Asian countries,” the study states.

Manuel Tena, group leader of the Networked Biomedical Research Center (CIBER) of Obesity and Nutrition in Spain, praises the study for “the power in the integration of data.” This data, however, has some limitations (which the authors themselves recognize), such as the lack of information in some countries or studies’ different criteria for identifying obesity and excess weight. “Certain interpretations must be taken with caution,” he says.

As this is a scientific review, Tena points out, the findings are not new, but rather “confirm the trend” found in smaller studies. One of these findings is that obesity is no longer just a problem in rich countries, but is expanding throughout the globe: in Ecuador, for example, the prevalence is 12%, in Mexico it is 16.5%, and in Kuwait it exceeds 20%.

For Tena, “the most worrying thing” is that the trend in children and adolescents continues to rise. The study analyzed the prevalence in two periods (between 2000 and 2011; and from 2012 to 2023) and concluded that, while in the first decade of the century, the prevalence of obesity was 7%, in the last 10 years, it reached 11.3%. “In some parts of the world, there are studies in adults where it is seen that trends are stabilizing. But in childhood obesity, the trend is growing and that means we are going down the wrong path,” explains Tena, who was not involved with the study.

“Unfortunately, we have not managed to stop this pandemic,” says Albert Goday, head of the Endocrinology section at the Hospital del Mar in Barcelona, who did not participate in the research either. “We have not been able to stop it, and it has great consequences for health,” he adds, warning: “We are seeing adult diseases in children.” According to Goday, the results of this study are “cause for serious concern”: “It is a prediction of what awaits us in the future. It is a prediction that the obesity pandemic is not going to be any better than it is now. The chance that a child with obesity will become an adult with obesity is high.”

Maternal obesity and smoking during pregnancy

The new research also breaks down the risk factors that play a role in the development of excess weight and obesity in childhood. To begin with, the prevalence is higher in boys than in girls. And maternal obesity and smoking during pregnancy also increase the risk of childhood and adolescent obesity. Maternal diabetes or gestational weight gain, on the other hand, showed an impact, but a more “modest” one, the authors point out. Regarding the influence of paternal obesity, which other studies considered a risk factor, this study’s findings “revealed otherwise.”

The study also directly points to the influence of environmental factors and specific behavioral and dietary patterns. Skipping breakfast, for example, was associated with a higher risk of pediatric obesity. And “surprisingly,” they added, eating more than three meals a day was linked to a lower risk, “which might be explained by the theory that having several small meals throughout a day is healthier than three large ones,” the study states.

The scientists also emphasize the vicious circle concerning lack of exercise: children with obesity practice less physical activity, which increases sedentary behaviors, which in turn, contributes to obesity development. “Our findings also showed that children with regular exercise had a much lower chance of obesity. Moreover, we observed that playing on the computer for more than two hours a day was associated with an increase in risk of excess weight, and time spent watching TV also showed a positive correlation, yet not significant,” the researchers explain.

The authors argue that screen time also increases the risk of obesity “via increased exposure to food marketing, increased mindless eating while watching screens, displacement of time spent in physical activities, reinforcement of sedentary behaviors, and reduced sleep duration.”

Tena emphasizes another key factor revealed by the scientific review: hours of sleep. “Having good sleep habits, such as sleeping 10 or more hours, reduces the risk,” he argues.

The gateway to other diseases

Obesity is, apart from a health problem in itself, a gateway to medium- and long-term chronic diseases. Children who are overweight are more likely to develop prediabetes, asthma, hypertension or fatty liver. The latter, if uncontrolled and persistent over time, can lead to cirrhosis or liver cancer. “Our research disclosed high prevalence of comorbidities in children and adolescents with obesity. The highest pooled prevalence was found in depression, which approximately one in three children with obesity might experience, followed by hypertension, with a pooled prevalence of 28%,” conclude the researchers, who argue that, in the treatment of obesity, these other associated diseases should be evaluated and treated simultaneously to prevent the conditions from worsening.

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