Is FTO useful for blood sugar?

The FTO variant (e.g., rs9939609) is primarily associated with increased BMI and obesity risk, not directly with blood sugar. Some studies show a weak link to type 2 diabetes, but this is largely mediated by BMI. The effect on fasting glucose is small (~0.06 mmol/L per risk allele) and clinically irrelevant. Direct-to-consumer tests often overstate the importance of single SNPs. Evidence is based on GWAS and population studies, not randomized controlled trials. A healthy lifestyle (exercise, diet, weight management) has a much greater impact on blood sugar than the FTO variant. Caveat: Without clinical context (fasting glucose, HbA1c, insulin resistance), the SNP is not actionable.