What you carry at this position in your DNA and what research says about it.
Obesity and Diabetes Risk: 7/10 evidence, 28 publications.
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Sample genotype (not yours): G/G
Typical Obesity and Diabetes Risk
This genotype is associated with a baseline risk for obesity and type 2 diabetes. It represents the most common genetic profile globally.
What this genotype means: Typical body mass index; Baseline risk for type 2 diabetes; Typical waist circumference.
Sample genotype (not yours): A/A
Increased Obesity and Diabetes Risk
Carrying two copies of the A allele is associated with a larger waist circumference, higher body weight, and increased risk of type 2 diabetes.
What this genotype means: Higher body mass index and body weight; Waist circumference increased by ~1.8 cm on average; Elevated risk for type 2 diabetes.
Sample genotype (not yours): G/A
Slightly Increased Obesity and Diabetes Risk
Carrying one copy of the A allele is linked to a slightly larger waist circumference and a modest increase in type 2 diabetes risk.
What this genotype means: Slightly higher body mass index; Waist circumference increased by ~0.9 cm on average; Modestly elevated risk for type 2 diabetes.
Gene function and biological role
Gene Function: The MC4R gene encodes the melanocortin-4 receptor, a vital G-protein coupled receptor expressed in the hypothalamus [1]. This receptor plays a central role in the brain's leptin-melanocortin signaling system, which regulates appetite, energy balance, and food intake [1]. Rare mutations in MC4R are the most common genetic cause of severe, early-onset monogenic obesity [2]. Common variants near the gene, while having smaller individual effects, are widely associated with common obesity and metabolic traits in the general population [2].
Variant Impact: The rs12970134 variant is an intergenic single nucleotide polymorphism located downstream of the MC4R gene on chromosome 18. Although it does not alter the protein sequence directly, it acts as a regulatory marker that influences MC4R expression and hypothalamic signaling [1]. The A allele is a well-documented risk factor for increased body mass index, waist circumference, and body weight [3]. It is also associated with elevated risk for type 2 diabetes and altered lipid metabolism [3].
Key Insight: The risk allele near MC4R is linked to higher dietary fat and total energy intake, suggesting it directly influences brain-derived appetite signals.
Location: MC4R. Chromosome 18 · 18q21.32 · 60.2 Mb
Estimated prevalence by population
Global 62.3%; European 54.1%; African 74.1%; East Asian 68.9%; South Asian 43.1%; Americas 68.7%; Ashkenazi 61.3%; Finnish 66.7%; Middle Eastern 54.0%; Amish 43.9%.
Estimated GG genotype frequency.
Global 32.8%; European 38.9%; African 24.0%; East Asian 28.2%; South Asian 45.1%; Americas 28.4%; Ashkenazi 34.0%; Finnish 29.9%; Middle Eastern 39.0%; Amish 44.7%.
Estimated GA genotype frequency.
Global 4.9%; European 7.0%; African 1.9%; East Asian 2.9%; South Asian 11.8%; Americas 2.9%; Ashkenazi 4.7%; Finnish 3.4%; Middle Eastern 7.0%; Amish 11.4%.
Estimated AA genotype frequency.
Showing effects for G/G genotype
Cardiovascular & Metabolic
Obesity & Body Composition
Obesity. Evidence: 7/10. Source: PMID 19079260. Typical Risk.
Waist Circumference. Evidence: 5/10. Source: PMID 18454146. Typical.
Diabetes & Glycemic Traits
Type 2 Diabetes. Evidence: 8/10. Source: PMID 22885922. Typical Risk.
Nutrition & Metabolism
Macronutrient Metabolism
Dietary Fat Intake. Evidence: 3/10. Source: PMID 27186233. Typical.
Showing effects for A/A genotype
Obesity. Evidence: 7/10. Source: PMID 19079260. Increased Risk.
Waist Circumference. Evidence: 5/10. Source: PMID 18454146. ~1.8 cm Larger.
Type 2 Diabetes. Evidence: 8/10. Source: PMID 22885922. Increased Risk.
Dietary Fat Intake. Evidence: 3/10. Source: PMID 27186233. Higher Intake.
Showing effects for G/A genotype
Obesity. Evidence: 7/10. Source: PMID 19079260. Slightly Increased.
Waist Circumference. Evidence: 5/10. Source: PMID 18454146. ~0.9 cm Larger.
Type 2 Diabetes. Evidence: 8/10. Source: PMID 22885922. Slightly Increased.
Dietary Fat Intake. Evidence: 3/10. Source: PMID 27186233. Slightly Higher.
What this genotype means for the people who carry it
Sample genotype: GG (Homozygous)
Carrying two copies of the G allele represents the typical genetic baseline for weight regulation and metabolic health. Large-scale genome-wide association studies show that this genotype is associated with a typical body mass index and waist circumference [1]. It does not carry the elevated risk for type 2 diabetes linked to the alternative variant [2]. Individuals with this profile generally experience typical appetite regulation and satiety responses [1]. While lifestyle factors like diet and exercise remain critical, this genetic background does not add extra susceptibility to metabolic challenges [2].
Typical body mass index; Baseline risk for type 2 diabetes; Typical waist circumference.
Sample genotype: AA (Homozygous)
Carrying two copies of the A allele is associated with the highest genetic predisposition to obesity and metabolic challenges at this locus. Studies show that individuals with this genotype have an adult waist circumference that is about 1.8 centimeters larger on average compared to those with the typical genotype [1]. This profile is also linked to significantly higher body mass index and overall body weight [2]. Furthermore, the risk of developing type 2 diabetes is elevated [3]. The genetic variation near the MC4R gene is thought to affect hypothalamic signaling, leading to increased appetite and a preference for energy-dense foods [4].
Higher body mass index and body weight; Waist circumference increased by ~1.8 cm on average; Elevated risk for type 2 diabetes.
Sample genotype: GA (Heterozygous)
Having one copy of the A allele is associated with a modest increase in body mass index and waist circumference [1]. Research indicates that each copy of the A allele increases adult waist circumference by approximately 0.9 centimeters on average [1]. This genetic variant is also linked to a slightly higher risk of developing type 2 diabetes [2]. The underlying mechanism may involve subtle changes in appetite regulation and a tendency toward higher dietary fat intake [3]. While the genetic influence is moderate, maintaining a balanced diet and active lifestyle can help mitigate these risks [2].
Slightly higher body mass index; Waist circumference increased by ~0.9 cm on average; Modestly elevated risk for type 2 diabetes.
Variants with shared genetic architecture
rs2229616 · MC4R Gene · Chr 18 · Obesity and Weight Control
rs571312 · MC4R Gene · Chr 18 · Obesity and Weight Risk
rs6567160 · MC4R Gene · Chr 18 · Weight and Obesity Risk
Common genetic variation near MC4R is associated with waist circumference and insulin resistance.
Content updated August 2026.
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