The study, conducted by a team at West China Second University Hospital of Sichuan University and registered prospectively with PROSPERO, followed the PRISMA 2020 reporting guidelines. The researchers searched eight databases, including PubMed, the Cochrane Library, Web of Science, Embase, and several Chinese-language databases, for records published up to 1 May 2026. From 2,189 initially retrieved articles, 18 studies ultimately met the inclusion criteria, comprising 16 cohort studies and two case-control studies. Most were conducted in China, Taiwan, the United States, Sweden, and Italy, with additional studies from the United Kingdom, South Africa, and the Netherlands.

For the asthma outcome, 12 studies with complete effect-size data were pooled using a random-effects model. The combined result showed that overweight and obesity were associated with increased odds of asthma incidence, with an odds ratio of 1.26 and a 95 percent confidence interval of 1.15 to 1.37. Heterogeneity across studies was high, with an I-squared value of 84 percent, prompting the authors to run formal subgroup analyses to identify its sources. Two factors emerged as statistically significant moderators: the region where a study was conducted and the sex of the participants.

The regional split was striking. In three large Taiwan-based studies, the association was weak, with an odds ratio of just 1.04, though the confidence interval of 1.01 to 1.06 still excluded the null. In the nine studies from other regions, the pooled odds ratio was 1.44, with a confidence interval of 1.29 to 1.62. The difference between the two regional subgroups was highly significant, with a P value for interaction below 0.001. The authors caution that this divergence may reflect methodological differences rather than biology: the Taiwan studies were large registry-based investigations using claims diagnostic codes, whereas most other-region studies were smaller and relied partly on self-reported asthma.

The sex-stratified findings were the study’s central contribution. Only two studies contributed data for male adolescents, yielding a pooled odds ratio of 1.07 with a confidence interval of 0.75 to 1.52, which crosses 1.0 and is therefore not statistically significant. Three studies contributed data for females, producing a pooled odds ratio of 2.11 with a confidence interval of 1.44 to 3.10. A formal interaction test confirmed that the association was significantly stronger in females than in males, with a ratio of odds ratios of 1.98 and a P value for interaction of 0.010. A within-study contrast restricted to the two studies reporting both sexes gave a similar result, with a ratio of odds ratios of 1.89.

The authors interpret this sex disparity through the lens of pubertal physiology, while stressing that the finding is exploratory. Adolescent females tend to accumulate more chest wall and visceral fat, which restricts thoracic mobility and reduces the lung’s dilatation reserve. Adipose tissue also secretes inflammatory mediators that sustain chronic low-grade systemic inflammation, and the authors suggest that estrogen’s regulatory effects on airway immunity during puberty may aggravate airway hyperresponsiveness. Males, by contrast, tend to carry more skeletal muscle and proportionally less fat, and androgens have been hypothesized to exert anti-inflammatory and bronchodilatory actions that could partially counteract obesity-related respiratory harm. The authors note that only two studies informed the male estimate, that asthma endpoints differed across contributing studies, and that evidence certainty was rated moderate for females but low for males, so larger sex-stratified studies are needed for validation.

Beyond asthma diagnosis, the meta-analysis examined pulmonary function using standardized mean differences, calculated as Hedges’ g, because the original studies reported lung volumes on incomparable scales and units. Six studies provided eligible group-level data for the volumetric outcomes. The overweight and obesity group showed significantly higher forced vital capacity, with a standardized mean difference of 0.35, and higher forced expiratory volume in one second, with a standardized mean difference of 0.23 that the authors describe as borderline significant. Crucially, the ratio of the two, FEV1 divided by FVC, was significantly lower in the overweight and obesity group, with a standardized mean difference of minus 0.27 and a confidence interval of minus 0.36 to minus 0.18.

This combination, larger lung volumes alongside a reduced FEV1/FVC ratio, is what the authors call an early obstructive pulmonary function pattern. They propose that excess thoracic and abdominal fat pushes the diaphragm upward and limits chest expansion, and that the lung may compensatorily increase vital capacity to sustain baseline ventilation, producing higher FVC and FEV1 readings. Meanwhile, obesity-related chronic low-grade inflammation may infiltrate the airway mucosa, promote smooth muscle hyperplasia and mucosal edema, and accelerate premature airway collapse during expiration, lowering the expiratory flow ratio. Notably, the direction of the FEV1/FVC effect was consistent across all six studies and remained robust in every leave-one-out sensitivity iteration, making it the most reliable pulmonary function signal in the analysis. The pooled FEV1 estimate, by contrast, lost statistical significance when any one of four individual studies was removed.

No significant differences emerged for peak expiratory flow, forced expiratory flow at 75 percent of FVC, or forced expiratory flow between 25 and 75 percent of FVC, and these outcomes rested on only one to four studies each with substantial heterogeneity. Unlike asthma, none of the pulmonary function outcomes showed a statistically significant sex interaction, although the authors emphasize that these tests had limited statistical power given the small number of sex-stratified studies, so modest sex differences cannot be excluded. Heterogeneity for FVC and FEV1 was very high, exceeding 95 percent, and a sensitivity analysis identified one large study using a percentage-predicted scale as the major source, with outcome scaling and population composition, rather than a single outlier, driving the variability.

The authors applied the GRADE framework to rate evidence certainty, assigning moderate certainty to four outcomes, including asthma in females and the FEV1/FVC reduction, and low certainty to seven others, including the overall asthma estimate. They acknowledge that all included studies were observational, so residual confounding cannot be excluded and the pooled estimates indicate associations rather than causal effects. Asthma endpoints also varied across studies, spanning incident asthma, prevalent asthma, asthma control, and wheeze. Publication bias analyses using Egger’s regression suggested small-study effects in the overall asthma pool, but these were largely attributable to the regional subgroup structure, and a trim-and-fill adjustment that added six hypothetical studies yielded a directionally stable adjusted odds ratio of 1.095. Based on the evidence, the authors suggest that adolescents with obesity, especially girls, could be prioritized for asthma screening, that routine examinations should include FEV1/FVC alongside FVC and FEV1, and that early weight management through diet and exercise may help reduce obesity-related asthma risk, while cautioning that screening thresholds require verification by high-quality, multiregional studies.

Subject of Research: Sex differences in the association of overweight and obesity with asthma and lung function in adolescents aged 10 to 18 years

Article Title: Sex differences in the association of overweight/obesity with asthma and lung function in adolescents aged 10–18 years: a meta-analysis

Article References: Wang, S., Zhang, Y., Huang, X., & Tian, Y. (2026). Sex differences in the association of overweight/obesity with asthma and lung function in adolescents aged 10–18 years: a meta-analysis. Frontiers in Pediatrics, 14, 1889125. https://doi.org/10.3389/fped.2026.1889125

Image Credits: AI Generated

DOI: 10.3389/fped.2026.1889125

Keywords: adolescent health, asthma, obesity, overweight, lung function, meta-analysis, sex differences, pulmonary function, FEV1/FVC, pediatrics, systematic review, public health