Childhood obesity is disproportionately affecting the poorest among us, a new study published in The European Journal of Public Health Thursday reaffirms.

Poring through population data from over 10,000 children in the United Kingdom, the researchers found that those in the lowest income bracket were twice as likely to be obese compared to the richest group of children at age 5 — at age 11, that risk jumped to nearly 3 times higher. Delving further, they found that this wide gap could largely be explained by other risk factors like the amount of time spent on physical activity or regularly eating breakfast. “These findings suggest that efforts to curb the increasing prevalence of obesity, particularly amongst disadvantaged children, should start early in life,” the researchers concluded.

That lower-income children are especially at risk of becoming overweight or obese is no secret. According to the Centers for Disease Control and Prevention, 14.2 percent of preschool aged children living in a household that earns 50 percent less than the annual poverty threshold are obese, compared to 11.8 percent of children belonging to a household that earns 151-185 percent above the the threshold (granted, that’s still not much annual income). Entangling the concrete reasons behind this increased risk, however, is a more difficult task.

Understanding Childhood Obesity

For this latest study, the researchers analyzed previous figures obtained from the UK’s Millennium Cohort Study (MCS), a nationally representative study of children born into 19,244 families from 2000 to 2002. Like other cohort studies, the MCS attempts to periodically collect extensive information on the habits and circumstances of its participants throughout the course of their lives, so that future researchers can try and identify the relationships between health outcomes like obesity and its potential risk factors.

After winnowing out those whose information wasn’t adequately recorded, the researchers were left with a sample of 11,965 children at age 5, and 9,384 at 11. For children belonging to the poorest fifth, or quintile, of households, 6.6 percent were obese at age 5 —  vs 3.5 for the richest fifth. At age 11, that shifted from 7.9 percent vs. 2.9 percent. As income level slid upward, the percentage of obese declined, but children in the “bottom, second, and third income quintiles were significantly more likely to experience upward movement across weight categories [from age 5 to 11] than children in the top quintile.”

“Multiple family health behaviors and environmental risk factors were relevant when attempting to explain income inequalities in overweight and obesity amongst children,” the authors reported. “The results suggest that both markers of physical activity and diet at ages 5 and 11 were particularly relevant in attenuating inequalities throughout childhood.”

Important too, however, were factors like the mother’s weight during pregnancy and her behaviors during early childhood. Different things mattered at different points of time, too, with fruit consumption and eating breakfast more associated with obesity at age 5 than 11, and the reverse being seen for playing sports more than 3 days a week at 11.

Because these factors only stacked up as time went on, the researchers believe that the best way to combat obesity to push or otherwise convince families to adopt healthier behaviors as soon as possible. Despite the urgency, the researchers caution against haphazardly promoting unproven public health strategies, though they do believe their study offers some potential directions to venture toward.

“Based on the findings of this study, interventions focusing on family physical activity and ‘healthier diets’ could be of benefit, for instance these could include family sport days, distribution of gym passes and cookery classes,” they offered.

Source: Goisis A, Sacker A, Kelly Y. Why are poorer children at higher risk of obesity and 10 overweight? A UK cohort study. The European Journal of Public Health. 2015.