The research team, led by Guillermo Barahona-Fuentes and Gerson Ferrari of Universidad de Santiago de Chile alongside Leandro F.M. Rezende of Universidade Federal de São Paulo, set out to address a persistent blind spot in global cancer epidemiology. Worldwide, approximately 37.8 percent of new cancer cases are attributable to modifiable risk factors, but the vast majority of that evidence originates from high-income countries in North America and Europe. Latin America, which records roughly 1.4 million new cancer cases and 670,000 cancer deaths each year, has historically been under-represented in international syntheses. Global burden studies often rely on extrapolations that may not capture the region’s specific exposure patterns, its dual epidemiologic burden of infection-linked malignancies such as HPV-driven cervical cancer and Helicobacter pylori-associated gastric cancer, and lifestyle-driven tumors of the breast, colorectum, and lung.

The methodology behind the new analysis was deliberately conservative. The researchers screened 984 records, whittling them down through title and abstract review and full-text assessment to 47 studies, 46 of which used case-control designs. Recognizing that pooling estimates across wildly different exposure definitions, cancer sites, and contrast categories can produce misleading numbers, the team restricted confirmatory quantitative meta-analysis to just two site-specific combinations where independent studies shared a homogeneous exposure construct. Everything else was summarized through a structured direction-of-effect synthesis, known as SWiM, in which each estimate is classified as harmful, protective, or null, and the consistency of direction is tested with exact binomial probabilities. This decision reflects a growing methodological awareness in evidence synthesis: a single pooled odds ratio generated from non-comparable constructs can obscure more than it reveals.

The two confirmatory pools yielded the study’s most precise quantitative findings. A higher score on the dietary inflammatory index, a measure of how strongly a person’s diet promotes systemic inflammation, was associated with increased prostate cancer risk in a meta-analysis of two independent samples, one from Argentina and one from Mexico, with a random-effects odds ratio of 1.38 (95 percent confidence interval 1.11–1.73) and moderate heterogeneity of 36 percent. Obesity, defined as a body mass index of 30 or higher, was associated with a sharply elevated risk of endometrial cancer, with a random-effects odds ratio of 3.81 (95 percent confidence interval 1.08–13.45), though the authors stress that this estimate is fragile because it rests partly on a 66-participant pilot study from Mexico. Mechanistically, the obesity-endometrial link is biologically plausible: excess adiposity promotes chronic systemic inflammation, hyperinsulinemia and insulin resistance, hormonal dysregulation, and perturbations of the gut microbiome, all of which reshape the tumor microenvironment.

The direction-of-effect synthesis across behavioral domains revealed patterns that were consistent even where pooling was impossible. Unhealthy dietary exposures, ranging from Western dietary patterns and pro-inflammatory diets to high chili pepper and capsaicin consumption and diets dominated by animal-origin and ultra-processed foods, were associated with increased cancer risk in 15 of 16 estimates, with a median odds ratio of 1.60 and a binomial probability of 0.0005. Healthy dietary exposures, by contrast, were protective in every single contributing estimate: nine out of nine, spanning phytoestrogens, folate, vitamin A, cinnamic acid polyphenols, vitamin D, prudent dietary patterns, mate and tea intake, and vegetarian diets, with a median odds ratio of 0.41 and a binomial p value of 0.0039. The consistency of this protective signal across six different cancer sites is among the most striking results of the analysis.

Tobacco smoking told a similarly coherent story, but in the opposite direction. Six of seven estimates indicated increased cancer risk, with a median odds ratio of 4.00 and a binomial p value of 0.0312. The strongest associations appeared for lung cancer, where ever-smokers faced roughly a fourfold increase in risk compared with never-smokers in a Mexico City study, and for esophageal cancer in a multinational IARC study spanning Argentina, Brazil, Paraguay, and Uruguay, where smoking carried an odds ratio of 3.24. Bladder cancer risk in Argentina was more than four times higher among ever-smokers. The single null result concerned cervical cancer, which after adjustment for other factors showed no independent smoking effect. Notably, the researchers corrected earlier syntheses that had treated male and female strata of the same multicenter study as independent, a subtle but important methodological refinement.

Alcohol consumption was consistently associated with elevated risk, particularly for cancers of the upper aerodigestive tract and esophagus, consistent with the classification of ethanol and its metabolite acetaldehyde as Group 1 carcinogens. In the multinational IARC study, ever-drinkers faced an odds ratio of 4.62 for oral cavity and upper aerodigestive tract cancers. Gastric cancer risk was more than doubled among the heaviest wine consumers in a Mexican study. Associations for breast and colorectal cancer were weaker and non-significant, and the authors emphasize that with only five estimates in the alcohol domain, these findings are exploratory. Physical activity showed a suggestive protective direction in all three available estimates, with a median odds ratio of 0.61, but the evidence base remains too thin for robust conclusions, a gap the researchers flag as a priority for future cohort research.

Underlying the headline findings is a stark data-quality problem that the study confronts head-on. The geographic concentration is extreme: 24 of the 47 studies were conducted in Mexico and 10 in Brazil, with Argentina contributing four and Uruguay, Chile, and Peru one each. Risk-of-bias assessment using the QUIPS tool classified 40 percent of studies as low risk, 53 percent as moderate, and 6 percent as high. Exposure measurement was a frequent concern, with two-thirds of studies rated moderate risk, largely because dietary intake was typically assessed with food-frequency questionnaires without documented validation. The authors also corrected several published estimates during their audit: a previously reported extreme gastric cancer odds ratio of 17.11 for the highest chili pepper consumption category was replaced with the study’s standardized any-versus-none contrast of 5.49, and a total fat estimate for endometrial cancer was corrected from 4.00 to a non-significant 1.19 after verification against the original publication.

The regional context amplifies the public-health significance of these associations. In several Latin American countries, more than 15 percent of adults smoke, often alongside occupational exposures and nutritional deficiencies that can potentiate carcinogen activation. Obesity affects more than 25 percent of adults regionally, and in Mexico, Chile, and Brazil more than 60 percent of adults carry excess body weight, a figure that has climbed steadily since the 1990s in parallel with a dietary transition replacing fresh and minimally processed foods with ultra-processed products. More than 40 percent of Latin American adults fail to meet minimum physical activity recommendations, and global per-capita alcohol consumption is projected to rise from 6.5 to 7.6 liters of pure alcohol per adult by 2030. Each of these trends pushes in the direction of greater cancer incidence, and the region’s lower five-year survival rates relative to high-income countries mean that prevention carries disproportionate value.

The authors argue that their findings support scaling up proven regional interventions, including Chile’s front-of-package warning labels, Mexico’s taxation of sugar-sweetened beverages, and Brazil’s tobacco control programs. They also lay out a minimum measurement agenda for future Latin American studies: reporting alcohol in grams per day with standardized beverage conversions, capturing binge versus regular drinking patterns, using lifetime abstainers rather than former drinkers as the reference group to avoid sick-quitter bias, and adopting a harmonized core set of confounders including age, sex, smoking status, and socioeconomic position. Building national cohorts, consolidating interoperable cancer registries and survey linkages, and committing to pre-registration and shared analysis code are described as essential steps toward reproducible, policy-relevant evidence.

While the authors caution that the predominantly case-control design of the included studies limits causal inference, and that findings from Mexico and Brazil may not generalize across a region marked by deep socioeconomic and health-system heterogeneity, the direction of the evidence is clear and aligns with global data. Tobacco, poor diet, alcohol, obesity, and inactivity are each modifiable, and the new synthesis demonstrates that the well-established links between these exposures and cancer observed in wealthy nations hold, in sometimes distinct patterns, across Latin America as well. For a region where cancer increasingly competes with infectious disease for health-system resources, the study provides what its authors describe as decision-relevant evidence: a quantified, region-specific case that prevention, from tobacco regulation to healthy food environments, is among the most powerful cancer-fighting tools Latin America possesses.

Obesity’s impact on cancer risk transcends simplistic calorie dynamics, involving multifaceted biological alterations including the dysregulation of sex hormone metabolism, imbalances in insulin signaling, and the persistence of chronic low-grade inflammation. These factors converge within the tumor microenvironment, creating conditions conducive to malignant transformation and growth. The review underscores the pivotal role of hyperinsulinemia, where elevated circulating insulin and insulin-like growth factors stimulate cellular proliferation, inhibit apoptosis, and potentiate cancerous processes, particularly in hormonally sensitive tissues such as the breast and endometrium.

Further deepening our mechanistic understanding, the review explores how adipose tissue is not merely an inert fat depot but a dynamic endocrine organ secreting a variety of bioactive molecules — adipokines and inflammatory cytokines — which modulate oncogenic signaling pathways. This endocrine function of adiposity supports a pro-tumorigenic state characterized by sustained inflammatory signaling and immune evasion, mechanisms that have been increasingly illuminated by recent advances in omics technologies.

The advent of multi-omics platforms integrating genomics, transcriptomics, proteomics, and metabolomics data has sparked a revolution in cancer research. These approaches have enabled the identification of novel biomarkers and mechanistic pathways linking obesity and tumor biology at an unprecedented resolution. They reveal, for instance, how specific genetic and epigenetic modifications in cancer cells are influenced by the adiposity-induced systemic environment, thereby prompting tumor heterogeneity and influencing responses to therapy.

Moreover, epidemiological studies now emphasize that adiposity and its cancer associations vary substantially by tumor subtype, signaling that the biological underpinnings differ across cancers categorized by their histology and molecular profiles. Such granularity compels a shift towards precision oncology that incorporates body composition metrics rather than relying solely on traditional measures such as BMI. Imaging-based assessments of adiposity distribution, including visceral and subcutaneous fat quantification through advanced radiological methods, are gaining traction as superior predictors of cancer risk and prognosis.

This emerging evidence crystallizes an urgent need for comprehensive biomarker-anchored strategies to elucidate causality and identify at-risk populations. Extending research efforts to encompass underrepresented groups, including populations from low- and middle-income countries, is essential. These populations often experience a disproportionate burden of obesity-related cancers but remain understudied due to resource constraints and systemic inequities in data collection.

Notably, this review accentuates the tremendous potential of novel obesity pharmacotherapies to transform cancer prevention paradigms. Current advances in medications capable of inducing substantial and sustained weight loss at scale represent a promising avenue to mitigate the obesity–cancer nexus. However, the landscape of obesity treatment continues to evolve, and rigorous clinical trials must evaluate whether these interventions translate into meaningful reductions in cancer incidence and mortality.

While lifestyle modification remains a cornerstone of obesity management, integrating pharmacological approaches with tailored prevention strategies could revolutionize public health efforts. Recognizing obesity as a chronic disease with far-reaching oncogenic consequences mandates a multidisciplinary response spanning oncology, endocrinology, epidemiology, and public health policy.

The review also emphasizes the critical role that chronic inflammation plays in the pathogenesis of obesity-associated cancers. Adipose tissue expansion induces inflammatory responses characterized by macrophage infiltration and cytokine secretion, which promote DNA damage and impair immune surveillance, fostering an environment ripe for tumor initiation and progression.

In addition, sex hormones modulated by adiposity are potent drivers of carcinogenesis, particularly in hormone-dependent cancers like breast, ovarian, and prostate cancer. Obesity alters the balance of estrogen and androgen production through peripheral conversion processes in adipose tissue, thus skewing hormonal homeostasis that can stimulate tumor growth and metastasis.

Notably, the interconnection between obesity, metabolic dysfunction, and cancer highlights the importance of insulin resistance as a link. Elevated levels of insulin and IGF-1 act as growth factors with mitogenic and anti-apoptotic properties, facilitating tumor development in various sites including the liver, colon, and pancreas, which are characteristically impacted by metabolic syndromes.

The authors recommend future research focus on integrating large-scale imaging and omics data sets, which would facilitate the unraveling of complex biological networks underpinning adiposity-driven carcinogenesis. These efforts would enable the identification of novel therapeutic targets and the refinement of patient stratification, paving the path towards personalized cancer prevention and treatment strategies.

In summary, excess adiposity is poised to become an even more formidable cancer risk factor in the coming decades, fueled by global trends in obesity prevalence. Addressing this burden requires a thorough mechanistic understanding, novel technologies, and equitable data capture to craft effective, scalable prevention and treatment modalities that can alter the trajectory of obesity-related cancers worldwide. This review crystallizes current knowledge while charting a visionary research agenda poised to transform the landscape of cancer epidemiology and therapeutic innovation in the 21st century.

Subject of Research: The biological mechanisms linking adiposity (obesity) with cancer development, epidemiological associations between excess adipose tissue and multiple cancer types, and emerging insights from advanced omics and imaging technologies.

Article Title: Adiposity and cancer: epidemiology, mechanisms and future perspectives.

Article References:
Watts, E.L., Gonzalez-Feliciano, A., Gunter, M.J. et al. Adiposity and cancer: epidemiology, mechanisms and future perspectives. Nat Metab (2026). https://doi.org/10.1038/s42255-026-01529-5

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s42255-026-01529-5