World Obesity Day provides an important opportunity to examine the many forces that shape obesity through a research‑based perspective, underscoring its complexity and lasting impact across life stages. This year, we highlight five studies from the BMC Series that explore how biological processes, individual behaviors, living environments, and social conditions contribute to obesity—from the earliest years of childhood through the profound physiological changes of pregnancy. Together, these studies reveal how factors such as early developmental exposures, access to supportive community spaces, dietary habits, physical activity patterns, and maternal health all converge to influence body composition and metabolic outcomes.

Association between obesity and mental health problems among Spanish children aged 9 and 12 years: the ELOIN study

BMC Public Health; https://link.springer.com/article/10.1186/s12889-026-26349-w

Childhood obesity continues to emerge as a significant predictor of psychological challenges, and findings from the ELOIN longitudinal study in Spain offer compelling evidence of this connection. Following more than 4,500 children aged nine and twelve, researchers observed a consistent association between higher body weight and increased emotional, behavioural, and social difficulties. Using standardized WHO classifications alongside parent‑reported Strengths and Difficulties Questionnaire (SDQ) scores, the study revealed that children with obesity exhibited notably higher levels of overall psychological distress.  

They scored significantly higher on total SDQ scales, with statistical analyses showing a β coefficient of 1.12, indicating a meaningful elevation in mental health difficulties compared with children of healthy weight. The research also identified elevated risks across emotional symptoms, conduct problems, and peer‑related challenges, with odds ratios reaching as high as 2.25 for peer issues—highlighting a pronounced social dimension to the psychological burden experienced by children living with obesity. Although girls appeared slightly more affected than boys, the difference did not reach statistical significance, suggesting that the psychological impact of obesity is broadly shared across genders. Overall, the findings emphasize that obesity in childhood extends far beyond physical health, influencing emotional resilience, social integration, and behavioral regulation during critical developmental years.

The impact of pre-pregnancy overweight/obesity on the birth weight of offspring born from women with polycystic ovarian syndrome

BMC Pregnancy and Childbirth; https://link.springer.com/article/10.1186/s12884-025-07755-1

This study published in BMC Pregnancy and Childbirth provides compelling evidence that pre‑pregnancy metabolic health plays a far more decisive role in determining neonatal birth‑weight outcomes than polycystic ovary syndrome (PCOS) itself. In a large nested case‑control study from Shandong University involving more than 8,000 singletons conceived through assisted reproductive technology, researchers set out to disentangle the independent effects of PCOS from those related to maternal weight status prior to conception. After applying propensity score matching to control for parental characteristics, offspring factors, and socioeconomic influences, the study revealed that elevated neonatal birth weight—including higher birth‑weight Z‑scores, birth‑weight‑to‑length ratios, and greater risk of macrosomia—was observed primarily among infants born to women with PCOS who entered pregnancy overweight or obese. In contrast, women with PCOS who had a normal pre‑pregnancy BMI gave birth to infants whose weight and growth indicators were statistically comparable to those of the non‑PCOS control group. Mediation analyses further strengthened these findings by demonstrating that pre‑pregnancy BMI exerted a significant influence on the association between PCOS and neonatal outcomes, indicating that metabolic disturbances linked to overweight and obesity—rather than PCOS itself—were responsible for the increased fetal growth seen in the cohort.

These results shift the clinical focus from PCOS as an isolated risk factor to the broader context of maternal metabolic health, underscoring the importance of targeted preconception weight management and early intervention strategies for women with PCOS. By optimizing metabolic status before pregnancy, it may be possible to mitigate risks such as macrosomia and improve both maternal and neonatal health outcomes, reinforcing the value of proactive, weight‑centered reproductive care.

Racial/ethnic disparities in the association of maternal diabetes and obesity with risk of preterm birth among 17 million mother-infant pairs in the United States: a population-based cohort study

BMC Pregnancy and Childbirth; https://link.springer.com/article/10.1186/s12884-025-07352-2

A comprehensive population‑based cohort analysis drawing on an extraordinary dataset of more than seventeen million mother–infant pairs in the United States offers one of the most detailed examinations to date of how maternal diabetes and pre‑pregnancy obesity influence the risk of preterm birth across ethnic groups. The study demonstrates that pre‑pregnancy diabetes consistently confers the highest likelihood of preterm delivery, regardless of ethnic background, establishing it as a powerful predictor of adverse birth timing. However, the degree of risk is far from uniform. The findings reveal considerable variation across groups, showing that structural and biological factors intertwine in complex ways. For example, non‑Hispanic Black women exhibited elevated preterm‑birth risk even when presenting with normal blood glucose and normal weight prior to pregnancy, indicating a baseline vulnerability that surpassed the risk observed in non‑Hispanic White women diagnosed with gestational diabetes. Among Asian and Hispanic women, the analysis showed a steady and significant increase in preterm‑birth likelihood as obesity class rose, suggesting that higher BMI intensifies vulnerability within these populations. These patterns underscore the interplay between metabolic health and systemic inequities, demonstrating that the same clinical conditions do not carry equal risk across demographic groups. The data point to the necessity of interpreting obesity‑ and diabetes‑related pregnancy outcomes within broader sociocultural and structural contexts rather than viewing them as purely biomedical phenomena. The study’s conclusions emphasize that improving maternal health outcomes will require care models capable of addressing metabolic risk while also acknowledging and counteracting ethnic disparities in healthcare access, treatment, and lived experience. Culturally responsive, equity‑centered prenatal strategies may therefore be essential for diminishing preterm‑birth inequalities and supporting healthier pregnancies across all communities

 Prevalence and Predictors of Overweight and Obesity Among School-Aged Children in the Country of Georgia: A Cross-Sectional Study, 2022

BMC Nutrition; https://link.springer.com/article/10.1186/s40795-024-00974-3

A 2022 analysis from the Childhood Obesity Surveillance Initiative (COSI) provides an in‑depth look at the growing burden of childhood overweight and obesity in Georgia, drawing on data from 3,334 schoolchildren across 245 schools. The findings reveal a concerning national pattern, with 17.2% of second‑grade children classified as overweight and an additional 11% meeting criteria for obesity. These trends were not evenly distributed across the population. Boys exhibited higher rates of excess weight than girls, and children living in urban areas faced a noticeably greater risk compared with those in rural regions, pointing to the influence of environmental and lifestyle conditions.

The study uncovered several key factors that strongly predicted weight status. Children who spent less time playing outdoors and those who traveled to school using passive modes of transportation, such as cars rather than walking, were more likely to fall into the overweight or obese categories. Parental characteristics also played a significant role—both parental education levels and parental body weight showed meaningful associations with children’s BMI, suggesting that family context and household health behaviors contribute significantly to childhood weight outcomes. Interestingly, the research did not identify substantial differences in dietary behaviors or screen‑time patterns between normal‑weight and overweight or obese children, indicating that the strongest predictors of excess weight were related to activity levels and the surrounding environment rather than food intake or media use. Taken together, the results emphasize that childhood obesity in Georgia is closely tied to the conditions in which children live, learn, and play. Urban design, opportunities for physical activity, transportation habits, and family health patterns all shape obesity risk, underscoring the importance of creating supportive environments that encourage movement, active commuting, and early preventive action.

Efficacy of an intervention in the nutritional status and consumption of ultra-processed foods in children with obesity treated in primary health care in Brazil

BMC Nutrition; https://link.springer.com/article/10.1186/s40795-025-01221-z

A randomized clinical trial conducted in primary health care units in Brazil provides valuable insight into how structured, sustained behavioral interventions can influence dietary habits among children with obesity. Involving children aged six to ten, the study implemented a nine month program that emphasized regular contact, family involvement, and targeted guidance aimed at reducing the consumption of ultra processed foods. The intervention group received a substantially higher level of engagement, with more than twenty six hours of structured activities and counseling sessions, compared with nine or fewer hours offered to the control group. This difference in exposure proved significant. Over the course of multiple follow up visits, children in the intervention group demonstrated consistent and meaningful reductions in their intake of ultra processed foods, signaling that intensive, community embedded support can effectively shift eating behaviors in a healthier direction.

Despite these improvements in dietary patterns, the study found no statistically significant change in BMI or BMI for age z scores during the intervention period, though evidence suggested that weight maintenance was achieved—a noteworthy outcome in pediatric obesity management, where continued weight gain is common. These findings point to an important insight: behavioral change often precedes measurable changes in body weight, and early shifts in food choices may serve as foundational steps toward long term health improvement. By demonstrating that primary health care settings can successfully engage families and children in meaningful dietary change, the study reinforces the value of community based, high contact interventions. It highlights that even in the absence of immediate reductions in BMI, the adoption of healthier eating habits—particularly reductions in ultra processed food consumption—can support more favorable health trajectories and lay essential groundwork for future weight related outcomes.

Open collections calling for submissions !

1. Impat of ultra-processed foods on nutritional quality- BMC nutrition
   https://link.springer.com/collections/debajheaac
2. Addressing obesity in older adults- BMC Geriatrics
   https://link.springer.com/collections/hdcieiadai
   
3. Healthcare service systems for obesity prevention and management- BMC Health Services Research
   https://link.springer.com/collections/gjdhchjgcf