FTO
Fat mass and obesity-associated protein
Gene Number: 79068
Location: 16q12.2
Key Functions: Energy balance regulation, appetite control, fat mass accumulation, obesity susceptibility
FTO is a gene involved in regulating RNA, the molecular instructions cells use to make proteins. Common variants in the FTO region are among the most widely studied genetic associations with body weight and obesity.
This page explores rs9939609 and rs1421085. The A allele at rs9939609 is associated with higher average body mass index (BMI), while research on rs1421085 helps explain how variation in this region can influence fat storage and energy use.
For more detail, read our FTO rs9939609 guide. You can also explore MC4R and appetite regulation.
SNP ID | Your Genotype | Alt Allele | Interpretation |
|---|---|---|---|
rs1421085 | Analyze your DNA to see your genotype | C | Analyze your DNA to see a personalized result. |
rs9939609 | Analyze your DNA to see your genotype | A | Analyze your DNA to see a personalized result. |
rs1421085 — Fat Storage and Energy Use
TT – Typical BMI and metabolic profile (R).
TC – Associated with ~1.3x increased obesity risk (R).
CC – Associated with ~1.7x increased obesity risk (R).
Functional effect: The C allele disrupts an ARID5B binding site, increasing IRX3 and IRX5 expression during fat-cell development. In experimental models, this favored energy-storing white fat cells over heat-producing beige fat cells (R).
rs9939609 — Body Mass Index and Obesity Susceptibility
TT – Common genotype; baseline BMI and metabolic response (R).
TA – Each A allele adds ~0.26 kg/m² BMI (~750 g) and ~0.51 cm waist; increases hunger, fat intake, and meal frequency (R).
AA – Homozygous risk; strongest overall effect on adiposity and obesity risk (R).
Functional effect: The A allele increases food intake and snacking behaviors across populations, raising obesity risk substantially; physical activity can attenuate (~80% reduction) its BMI effect (R).
Understanding the two results together
These variants are often inherited together, particularly in people of European ancestry. They can therefore reflect overlapping genetic information; their effects should not simply be added or multiplied.
Does lifestyle still matter?
Yes. A meta-analysis involving more than 218,000 adults found that the excess odds of obesity associated with FTO variants were approximately 27% smaller in physically active adults than in inactive adults [R]. This describes a difference between study groups, not a guaranteed reduction in an individual’s risk.
Learn more about FTO, appetite, and BMI, or explore MC4R, another region associated with body-weight regulation.
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