Childhood obesity has become one of the most serious public health challenges of the 21st century. According to the World Health Organization, in 2022, more than 39 million children under the age of 5 were overweight or obese worldwide, with a high economic impact ^1–3. In Latin America, childhood overweight rates have risen sharply in the past two decades, with early childhood (0-5 years) being a particularly vulnerable window for the establishment of long-term metabolic programming ⁴. In Colombia, national nutrition surveys have shown increasing trends in early childhood overweight and obesity, disproportionately affecting urban and low-income populations⁵. Obesity in early life results from a complex interplay of genetic, epigenetic, environmental, and behavioral factors ⁶. At the physiological level, key contributors include altered appetite regulation, impaired energy expenditure, and insulin resistance⁷ . Mitochondrial dysfunction has also been implicated, leading to inefficient oxidative phosphorylation and increased lipid storage ⁸ . Dysregulation of adipose tissue signaling, including leptin and adiponectin pathways, may further disrupt energy homeostasis⁹ . In infants and toddlers, these disturbances can be exacerbated by early-life exposures, such as maternal overnutrition, gestational diabetes, and suboptimal breastfeeding practices^10–12.

Exposure to high-altitude environments (typically above 2000 meters above sea level) introduces a hypobaric hypoxic condition that affects oxygen delivery, metabolic rate, and systemic physiology¹³ . Several studies have hypothesized that altitude may exert protective metabolic effects, including increased basal energy expenditure, altered appetite-regulating hormones (e.g., ghrelin, leptin), and upregulation of genes associated with oxidative metabolism¹⁴ . However, an increase in insulin resistance may reduce the favorable effect of high altitude ¹⁵ . Research in adults from Peru, Bolivia, and Tibet has shown a lower prevalence of obesity and metabolic syndrome at higher altitudes. However, similar evidence in children, particularly those under 2 years old ^{6 16 17}, is scarce and contradictory. A constellation of maternal, environmental, and developmental factors influences the risk of obesity in early childhood. Studies in Latin American countries such as Ecuador, Peru, and Argentina have reported conflicting findings regarding the association between altitude, obesity, and growth in children aged 0–5 years¹⁸. In Ecuador, research comparing children residing in urban highland areas (2,772 meters) with those in coastal regions (605 meters) found that highland children exhibited lower height-for-age and weight-for-age Z-scores, with stunting and underweight rates increasing by factors of four and three, respectively ¹⁹ .

In Peru, studies have utilized an altitude threshold of 2,500 meters to differentiate settings. One study found that living at altitudes below 2,500 meters was associated with a 2.67-fold higher likelihood of obesity. Additional reports highlighted significant regional disparities: obesity prevalence reached 10.1% in more urbanized areas like Lima, while it dropped to 2.6% in rural jungle regions²⁰.

In Argentina, children residing at altitudes above 2,500 meters were found to be shorter and lighter than their counterparts in low-lying areas. Still, they had higher body mass index (BMI), ponderal index, and surface area-to-body mass ratios²¹. Age-specific analyses revealed that stunting was most pronounced before 24 months of age, and obesity rates were elevated during the first year of life. The socioeconomic context further influenced these patterns: urban environments at higher altitudes with lower poverty rates were associated with higher obesity prevalence, whereas poverty in highland areas was linked to chronic malnutrition²².

Multiple risk factors, including maternal obesity and metabolic status during pregnancy, quality of prenatal nutrition, maternal education, socioeconomic level, breastfeeding duration, and exposure to obesogenic environments, may influence obesity in early childhood. The “developmental origins of health and disease” (DOHaD) hypothesis suggests that intrauterine and early postnatal exposures program long-term metabolic outcomes^{23 24}. Thus, investigating how these risk factors interact with altitude may help to explain observed geographical disparities in obesity prevalence.

In this ecological study²⁵, we analyzed data from 1,123 municipalities across Colombia to explore whether altitude is associated with the prevalence of obesity in children under five years of age. Using national health surveillance data and population estimates, municipalities were stratified into four altitude ranges (<1,000 m; 1,000–1,999 m; 2,000–2,499 m; and ≥2,500 m). We found that the prevalence of childhood obesity was highest in low-altitude municipalities (≥6%) and decreased consistently with elevation, reaching a minimum in regions above 2,500 meters. This trend remained significant after stratifying by population size and examining department capitals. Our findings suggest that living at high altitude may confer a protective effect against early childhood obesity, likely mediated by both physiological adaptations and socioeconomic gradients.