Background

We have reported lower prevalence of obesity (defined as a body mass index (BMI) ≥30 kg/m²) in populations from higher altitudes. One of the limitations of BMI is that it does not distinguish between fat mass and non-fat mass. Thus, it is unclear whether the prevalence of high body adiposity is lower at higher altitudes.

Methods

We analyzed data from adult participants (≥20 years of age) from Peru (National Household Survey 2009−2010) and Mexico (Mexican Family Life Survey 2009−2012). Whole-body fat percentage was estimated by the recently developed and validated anthropometric equation RFM (Relative Fat Mass), which is based on the height/waist circumference ratio. Body weight, height and waist circumference were measured using standardized procedures. RFM-defined obesity was diagnosed if RFM was ≥40% in women (that is, ≥40% body fat) and ≥30% in men.

Results

Final dataset for analysis comprised 36,134 Peruvians (mean age, 41.9 years; 49.8% women) and 16,376 Mexicans (mean age, 45.8 years; 70.2% women). Among Peruvians, the overall prevalence of BMI-defined obesity and RFM-defined obesity was 17.0% and 42.0%, respectively. Among Mexicans, the overall prevalence of BMI-defined obesity and RFM-defined obesity was 35.6% and 65.3%, respectively. The odds ratio (OR) for RFM-defined obesity was 0.66 (95% CI, 0.59−0.74; P<0.001) among Peruvians who lived at or above 1,500 m altitude (4,921 ft) (n=14,732) compared with those who lived below 250 m (820 ft) (n=14,201), adjusting for age, sex and urbanicity. Likewise, the adjusted OR for RFM-defined obesity was 0.73 (95% CI, 0.55−0.97; P=0.028) among Mexicans who lived at or above 1,500 m (n=6,320) compared with those who lived below 250 m (n=5,216).

Conclusions

In the populations studied, body adiposity was inversely associated with altitude. Whether this inverse association is explained by altitude-related factors per se (e.g. hypoxia, cold) or lifestyle differences warrants further investigation.