Population trends in nutritional status and socioeconomic divergence in extreme obesity in Peru: geospatial dynamics and intergenerational risk

Peru is undergoing a sustained nutrition transition; however, evidence on the simultaneous behavior of extreme phenotypes — geriatric underweight and class III obesity — and their generational determinants remains limited. We aimed to analyze the temporal, geospatial, socioeconomic, and intergenerational dynamics of population malnutrition over the last decade. This was a repeated cross-sectional, population-based analytical trend study with age–period–cohort (APC) analysis, using data from the Peruvian Demographic and Family Health Survey (DHS) 2014–2024 (excluding 2020), including 257,264 individuals aged ≥15 years. Nutritional status was assessed using body mass index (BMI) and life-stage–specific cut-offs (adolescents: 2007 World Health Organization BMI-for-age Z-scores; adults: World Health Organization BMI criteria; older adults: Pan American Health Organization/Salud, Bienestar y Envejecimiento and Peruvian Ministry of Health criteria). Temporal trends were estimated using average annual percent change (AAPC) from weighted log-linear regressions. Economic inequality was quantified with the Erreygers Concentration Index (ECI). Generational risk was estimated through an APC model restricted to adults aged 20–80 years for class III obesity (BMI ≥40 kg/m 2 ). Among adults, normal weight prevalence fell markedly (AAPC −3.4%/year; p < 0.001), while class III obesity showed the largest proportional increase (+8.9%/year; p < 0.001). Underweight remained close to 20% in older adults by 2024, reflecting a persistent geriatric double burden. ECI showed that extreme obesity, initially concentrated in wealthier quintiles, spread toward lower and middle strata, though the pro-rich gradient persisted (ECI 2014: 0.008; ECI 2024: 0.011; both p = 0.002). Cohorts born in the 1990s and 2000s showed substantially higher relative rates of class III obesity compared with the 1970 reference cohort at equivalent biological age, reflecting a marked unfavorable generational shift. Peru exhibits a divergent double burden of malnutrition. The rise in class III obesity spans multiple socioeconomic strata, disproportionately affects recent cohorts, and coexists with persistently high underweight in the geriatric population.