---
title: "Infant Infections and Later Childhood Weight Gain and Obesity in Southern California"
id: "cdc-emerging-infectious-diseases-journal-1-infections-in-infancy-and-association-with-long-term-weight-gain-and-obesity-in"
canonical_url: "https://medichelpline.com/clinical-feed/cdc-emerging-infectious-diseases-journal-1-infections-in-infancy-and-association-with-long-term-weight-gain-and-obesity-in"
content_type: "clinical_feed_article"
specialty: "Infectious Disease"
source_name: "CDC Emerging Infectious Diseases Journal"
source_url: "https://wwwnc.cdc.gov/eid/article/32/8/24-1522_article"
published_at: "2026-07-25T04:00:00.000Z"
evidence_level: "Agency Feed"
license: "CC-BY-NC-4.0 / Informational Use"
---
# Infant Infections and Later Childhood Weight Gain and Obesity in Southern California
## Provenance & Clinical Metadata
- **Canonical URL:** https://medichelpline.com/clinical-feed/cdc-emerging-infectious-diseases-journal-1-infections-in-infancy-and-association-with-long-term-weight-gain-and-obesity-in
- **Specialty:** [Infectious Disease](https://medichelpline.com/clinical-feed/infectious-disease.md)
- **Primary Source:** CDC Emerging Infectious Diseases Journal
- **Source URL:** [Original Journal Publication](https://wwwnc.cdc.gov/eid/article/32/8/24-1522_article)
- **Published At:** 2026-07-25T04:00:00.000Z
- **Evidence Rating:** Agency Feed
## Executive GIST (TL;DR)
- This retrospective cohort study evaluated whether **medically attended infections in infancy** (birth cohort 2008–2012) are associated with later weight outcomes (absolute weight and obesity) at ages 4–6 and 10–15 years within the Kaiser Permanente Southern California population. - The study excluded low birthweight ( 2 weeks apart were counted separately; multiple diagnoses within 2 weeks were one infection. - Outcomes were obesity (BMI >95th percentile) and absolute weight (kg) measured closest to age 5 for the 4–6 year group and closest to age 10 for the 10–15 year group. BMI was standardized by age and sex using CDC growth charts; absolute weight was used to convey clinically meaningful differences. - Antimicrobial exposure was classified as narrow-spectrum (amoxicillin, penicillin, first-generation cephalosporin, or combinations) versus broad-spectrum (any other agent or combination). Timing (<6 vs 6–12 months), frequency (number of infections and courses), and timing of first antimicrobial were recorded. - The abstract reports that infants with early clinical infection had higher rates of obesity at both 4–6 and 10–15 years, with a dose–response by number of infections and corresponding significant weight increases. Most infections were viral. Antimicrobial treatment was less predictive of weight outcomes than infection diagnosis. - The investigators found a correlation between infections diagnosed in infancy and later weight outcomes but stated they could not determine causation. Details of statistical models, effect sizes, confidence intervals, and complete results are not reported in the provided source text. - The study contextualizes findings against prior literature showing mixed associations of early infections and antimicrobial exposures with later BMI and obesity, and notes potential confounding by care-seeking behavior and antimicrobial use.
## Clinical Analysis & Structured Key Points
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[EID Journal](https://wwwnc.cdc.gov/eid/) 2. [Volume 32](https://wwwnc.cdc.gov/eid/early-release) 3. [Early Release](https://wwwnc.cdc.gov/eid/early-release#issue-1343) 4. [Main Article](https://wwwnc.cdc.gov/eid/article/32/8/24-1522_article) * [Facebook](https://www.facebook.com/sharer/sharer.php?u=%2Feid%2Farticle%2F32%2F8%2F24-1522_article "Share to Facebook") * [Twitter](http://twitter.com/share?url=%2Feid%2Farticle%2F32%2F8%2F24-1522_article&text= "Share to Twitter") * [LinkedIn](https://www.linkedin.com/shareArticle?url=%2Feid%2Farticle%2F32%2F8%2F24-1522_article&title= "Share to LinkedIn") * [Syndicate](https://tools.cdc.gov/medialibrary/index.aspx#/sharecontent//eid/article/32/8/24-1522_article "Embed this Page") [ Emerging Infectious Disease journal ISSN: 1080-6059 ](https://wwwnc.cdc.gov/eid/) _Disclaimer: Early release articles are not considered as final versions. Any changes will be reflected in the online version in the month the article is officially released._ #### Volume 32, Number 8—August 2026 ##### _Research_ ### Infections in Infancy and Association with Long-Term Weight Gain and Obesity in Children, Southern California, USA On This Page [Methods](https://wwwnc.cdc.gov/eid/article/32/8/24-1522_article) * * * [Results](https://wwwnc.cdc.gov/eid/article/32/8/24-1522_article) * * * [Discussion](https://wwwnc.cdc.gov/eid/article/32/8/24-1522_article) * * * [Cite This Article](https://wwwnc.cdc.gov/eid/article/32/8/24-1522_article) Figures [Figure 1](https://wwwnc.cdc.gov/eid/article/32/8/24-1522-f1) * * * [Figure 2](https://wwwnc.cdc.gov/eid/article/32/8/24-1522-f2) * * * [Figure 3](https://wwwnc.cdc.gov/eid/article/32/8/24-1522-f3) * * * [Figure 4](https://wwwnc.cdc.gov/eid/article/32/8/24-1522-f4) Tables [Table 1](https://wwwnc.cdc.gov/eid/article/32/8/24-1522-t1) * * * [Table 2](https://wwwnc.cdc.gov/eid/article/32/8/24-1522-t2) * * * [Table 3](https://wwwnc.cdc.gov/eid/article/32/8/24-1522-t3) Downloads [Article ](https://wwwnc.cdc.gov/eid/article/32/8/pdfs/24-1522.pdf) * * * [RIS [TXT - 2 KB] ](https://wwwnc.cdc.gov/eid/article/32/8/24-1522.ris) Article Metrics [Metric Details](https://wwwnc.cdc.gov/eid/article/32/8/24-1522_article) Zackary W. Taylor[![Comments to Author](https://wwwnc.cdc.gov/eid/content/images/icon/email.gif)](https://wwwnc.cdc.gov/eid/article/32/8/24-1522_article#comment) and Jane C. Lin Author affiliation: Kaiser Permanente Southern California at KP Los Angeles Medical Center, Los Angeles, California, USA (Z.W. Taylor); Kaiser Permanente, Pasadena, California, USA (J.C. Lin) [Cite This Article](https://wwwnc.cdc.gov/eid/article/32/8/24-1522_article "Show Article Citations") Open modal [Citation for Media](https://wwwnc.cdc.gov/eid/press) ### Abstract Chronic obesity is a growing public health threat in the United States; >40% of adults are affected. We retrospectively assessed the frequency of medically attended infection in infants born during 2008–2012 relative to absolute weight and body mass index outcomes at age 4–6 years of age and 10–15 years of age. Multivariable regression revealed those with early clinical infection had higher rates of obesity at 4–6 years and 10–15 years than those without, proportional to the number of infections diagnosed and corresponding to significant weight increases. Compared with infants whose infections were not treated with antimicrobial drugs, treatment was less predictive of weight outcomes. Most infections were viral. Our investigation found a correlation between infections diagnosed in infancy and later weight outcomes, but we could not determine the cause. Obesity is a major public health threat in the United States; >40% adults are affected, and obesity is a risk factor for chronic diseases such as diabetes and heart disease ([_1_](https://wwwnc.cdc.gov/eid/article/32/8/24-1522_article#r1 "1")). Obesity itself is also recognized as a chronic disease that has a cumulative relation to mortality that is especially marked when starting earlier in life ([_2_](https://wwwnc.cdc.gov/eid/article/32/8/24-1522_article#r2 "2")–[ _4_](https://wwwnc.cdc.gov/eid/article/32/8/24-1522_article#r4 "4")) or prolonged over a decade ([_5_](https://wwwnc.cdc.gov/eid/article/32/8/24-1522_article#r5 "5")). Childhood obesity is a growing problem; ≈1 in 5 children and adolescents are now obese ([_6_](https://wwwnc.cdc.gov/eid/article/32/8/24-1522_article#r6 "6")), and adolescent obesity frequently leads to adult obesity. Chronic obesity, although traditionally thought of as a condition of choice, is socioeconomically, genetically, and biologically driven, with complicated and multifactorial roots emphasized in US medical practice guidelines ([_7_](https://wwwnc.cdc.gov/eid/article/32/8/24-1522_article#r7 "7")). Infections are well-established drivers of other chronic diseases, and a well-recognized link between infections and long-term weight loss (e.g., tuberculosis, parasites) belies a less self-explanatory link between early viral infection and long-term weight gain and obesity, observed in the United States and globally. This link between infection and long-term weight gain was observed in a longitudinal prospective study of in the Philippines ([_8_](https://wwwnc.cdc.gov/eid/article/32/8/24-1522_article#r8 "8")) observed from infancy. The participants in that study were followed under the hypothesis that early infections and other adverse conditions in infancy and early childhood would be correlated with long-term decreased weight relative to uninfected patients, but a correlation of prospectively reported early upper respiratory infections with long-term increase in body mass index (BMI) as adults was observed. Infection-related antimicrobial drug exposure was a possible explanation for the increased BMI finding. The study did not control for antimicrobial drug use, and antimicrobial drugs have been associated with weight gain and obesity ([_9_](https://wwwnc.cdc.gov/eid/article/32/8/24-1522_article#r9 "9")–[ _12_](https://wwwnc.cdc.gov/eid/article/32/8/24-1522_article#r12 "12")). However, a subsequent large retrospective study in the United States revealed early antimicrobial drug exposure to be a proxy for early infection and association with obesity, rather than the opposite. Medically attended infections in infancy, defined as infections for which medical care was sought, were shown to be independent predictors of obesity, and the risk of obesity increased in proportion to the number of diagnosed infections ([_13_](https://wwwnc.cdc.gov/eid/article/32/8/24-1522_article#r13 "13")). Within that study, the correlation with medically attended infections in infancy and long-term obesity was also confirmed in a subset of same-sex twins with discordant infection and antimicrobial drug exposure status, corroborating the observed correlation by nullifying parental care-seeking behavior and other parental confounders. The correlation of early antimicrobial drugs and obesity in humans, observed previously in many retrospective studies, might not have been observed if previous studies had controlled for the underlying infections; any conclusion that antimicrobial drug use in infancy leads to obesity could be erroneous. The use of obesity as the outcome variable in those retrospective studies has also been questioned. A change in the rate of obesity, rather than absolute weight, is usually used to depict clinically notable weight change in a population, because obesity is associated with meaningful health outcomes. However, obesity diagnosis is made on the basis of a BMI threshold, which has been discounted as a possible self-confounder in regression analysis ([_14_](https://wwwnc.cdc.gov/eid/article/32/8/24-1522_article#r14 "14")), favoring absolute weight velocity as an alternative to BMI. In our population of children at Kaiser Permanente Southern California Kaiser (KPSCAL), we sought to confirm the previously observed association of childhood infections in infancy with weight increase and obesity later in childhood, to analyze the magnitude of the absolute weight increase, and to find whether absolute weight differences are commensurate with obesity rate differences. Antimicrobial drug use is a possible confounder for infection, including viral infections during which antimicrobial drugs are often prescribed, so antimicrobial drug–treated infections were assessed separately. ### Methods ##### Population and Study Design Figure 1 ![Flowchart for inclusion or exclusion of children in retrospective study of infant infections and obesity in children, southern California, USA. BMI, body mass index.](https://wwwnc.cdc.gov/eid/images/24-1522-F1-tn.jpg) [Figure 1](https://wwwnc.cdc.gov/eid/article/32/8/24-1522-f1 "Figure 1"). Flowchart for inclusion or exclusion of children in retrospective study of infant infections and obesity in children, southern California, USA. BMI, body mass index. Our study identified a retrospective, longitudinal cohort of infants born 2008–2012 in the KPSCAL system. Among that birth cohort, we excluded patients with low birthweight (weight 95%) and absolute weight (kg), as measured at age 4–6 years of age, 10–15 years of age, or both. We used BMI and absolute weight closest to age 5 for those 4–6 years of age and age 10 for those 10–15 years of age. We standardized BMI by the age and sex of the child on the basis of Centers of Disease Control and Prevention growth charts by using the associated macro ( ). We used absolute weight rather than standardized weight (z-score) specifically because absolute weight differences are more readily understood and communicated in terms of clinical importance. We accounted for weight differences related to sex and height by including those variables in multivariable analysis and accounted for age by separation into 2 discrete age groups. We divided patients into 3 groups: those with no medically attended infections in the first year of life (NMAI); those with medically attended infections without antimicrobial drug treatment (IWOT); and those with _>_ 1 medically attended infections with antimicrobial drug treatment (IWAT). Antimicrobial drug use was thereby removed as a possible confounder in the NMAI versus IWOT comparison, enabling us to gauge the association of infection with risk for weight gain and obesity, independent of antimicrobial drugs. We compared the IWOT group to the IWAT group to determine any additional contribution of antimicrobial drugs to weight outcomes. We also assessed the frequency of medically attended infection in infancy ( 1 instance in the IWAT group and recorded the number of infections in that group separately from the number of antimicrobial drug courses. We considered infections recorded >2 weeks apart separate infections, and if there were multiple infection diagnoses within a single 2-week period, even with differing International Classification of Diseases, 9th Revision, codes, they were counted as a single clinical infection. We defined narrow-spectrum antimicrobial drug exposure as exposure to only amoxicillin, penicillin, a first-generation cephalosporin, or any combination of those. We defined broad-spectrum antimicrobial drug exposure as exposure to any other antimicrobial drug or combination in infancy (<12 months of age), whether or not the patient also received a narrow-spectrum antimicrobial drug. The KPSCAL healthcare system is a large, comprehensive healthcare model, with clinics and hospitals throughout Southern California providing inpatient and outpatient care, incorporating primary and subspecialty care to minimize the need to seek care outside the system. Although care might not be captured on the KPSCAL electronic medical record (EMR) if patients get care while traveling outside southern California, and some KPSCAL patients do get contracted outside care for certain highly specialized procedures (e.g., transplants during the acute transplant period, pediatric cardiothoracic surgery), member patients otherwise obtain healthcare within KPSCAL, including
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