Obesity during adolescence is significantly associated with socioeconomic status and genetic factors, but the contribution of dietary intake and physical activity is conflicting, a review of 40 published studies shows.
Noting that literature on the multiple factors linked to childhood obesity is limited, researchers said further studies are needed to develop effective strategies and interventions to prevent obesity during adolescence.
The study, “Behavioral, contextual and biological factors associated with obesity during adolescence: A systematic review,” was published in the journal PLOS One.
Childhood obesity is among the major public health challenges of the 21st century. From 1975 to 2016, the number of obese children and adolescents increased by 11 times – from 11 million to 124 million, the researchers said.
Since obesity stems from a long-term energy imbalance — when people eat more than they waste — prevention and treatment interventions have been mainly focused on changes that improve eating habits, increase physical activity, and reduce sedentary behaviors.
However, obesity is caused by a complex and not fully understood interaction between genetic, environmental, and behavioral factors, meaning that behavioral changes alone might not be sufficient to treat obesity.
To better understand the factors that influence obesity in adolescents, researchers at the University of Beira Interior in Portugal, and their colleagues, reviewed published studies focusing on biological, socioeconomic, and behavioral factors associated with obesity in adolescents ages 10 to 18.
From a total of 5,146 studies published between 2000 and 2018, only 40 were included in the analysis. Eight of those studies were conducted in Australia, 10 in Europe, and 15 in North America.
The number of participants ranged from 103 to 7,090, with follow-up from one to 18 years. The majority of the studies included both girls and boys, with two including only girls, and one only boys.
Researchers focused on the link between obesity and behavioral factors — type of dietary intake, whether children had been breastfed, physical activity, sedentary behavior, and sleep — socioeconomic status, and genetic factors.
Only socioeconomic and genetic factors had evidence linking them to obesity, with studies assessing dietary intake, physical activity, sedentary behavior, and sleep, providing conflicting results.
In one study, researchers found that girls from families with a low socioeconomic status were at higher risk of becoming obese, while a higher socioeconomic position predicted that boys would cease to be obese.
Three studies focused on the link between genetic factors and obesity. One found that genetic variants of two genes — FTO and MC4R — were associated with body mass index, a measure of body fat. Another study reported that overweight children were more likely to become obese, and less likely to exit obesity, if they had an obese parent.
“[W]e found a positive consistent association between genetic factors and obesity during adolescence,” the researchers said.
However, “these findings should be interpreted with caution due to the heterogeneity and small number of studies identified,” they added.
Since the evidence was either conflicting or limited for the remaining factors, there is a need for further studies evaluating which factors play a role in obesity during adolescence, they said.
“Inaccurate dietary assessment may comprise a serious obstacle to understand the impact of dietary intake on the development of obesity,” the researchers said. “Therefore, continued efforts towards improving self-reported methods, as well as the use of technological advances to develop new methods to improve dietary assessment are crucial in the field of nutrition research.”