The association between variants in the fat mass and obesity associated (FTO) gene on chromosome 16q12.2 and body mass index (BMI) is well-established in populations of European descent. Genome-wide association studies (GWAS) and subsequent replication studies have identified several strongly correlated single nucleotide polymorphisms (SNPs) located in intron 1 of FTO associated with increased BMI and increased risk of obesity [1]–[13]. With an observed effect size of 0.35 kg/m2 (0.1 z-score units of BMI) per risk allele, the FTO locus has a substantially stronger effect on BMI than any other identified common locus [14]. While this impact on BMI may seem small, it has a potential public health bearing, as even a 1 unit increase in BMI results in an estimated 8% increase in coronary heart disease [15], and excess weight in midlife is associated with increased mortality [16]. Thus, a seemingly small increase in BMI can have a marked impact, particularly in countries with an increasing burden of excess weight, such as the US, where an estimated 68% of adults were overweight or obese in 2008 [17].
