Adiponectin is an adipose tissue-specific hormone that is commonly decreased in obese subjects. Furthermore, single-nucleotide polymorphisms (SNPs) of the adiponectin gene have been associated with metabolic phenotypes. The present study investigated whether the adiponectin gene promoter variant -11391 G/A (rs17300539) could predict the risk of developing traits characterizing the metabolic syndrome (MetS) and the impact of weight management. The -11391 G/A SNP was genotyped in 180 Spanish volunteers (BMI: 31.4+/-3.2 kg/m (2); age: 35+/-5 years). Clinical measurements were determined at baseline, following an 8-week low-calorie diet (LCD), and at 32 and 60 weeks. At baseline, the GG genotype was associated with higher HOMA-IR, insulin and triacylglyceride concentrations than other genotypes (p<0.05) and was also related with a higher risk of insulin resistance (OR: 2.437, p=0.025) and MetS clinical manifestations (OR: 3.236, p=0.003). Following the LCD, the increased risk in GG subjects compared with others disappeared (p>0.05). By 32 weeks after dietary therapy (n=84), GG carriers had recovered the risk of metabolic comorbidities (OR: 2.420, p=0.043). This risk was even more evident after 60 weeks (OR: 2.875, p=0.014). These data show an increased risk of insulin resistance and MetS complications in obese subjects of the -11391 GG genotype. The risk was markedly reduced during an energy-restricted diet, but was not sustained. Carriage of the A allele therefore confers protection from weight regain, and the effect is particularly evident 32-60 weeks after the dietary intervention, when improvement in GG subjects had disappeared.