Influence of reward-related genetic variants on BMI and predisposition to obesity: Systematic review and meta-analysis

Figures

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  Figure 1 -. Flow diagram of the article screening process using PRISMA guidelines. Adapted from: Page et al. (2021).

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  Figure 2 -. Geographic distribution of the 117 studies included in the systematic review. The articles included in the review originate from 34 countries, which are highlighted in blue on the map. No studies from the African continent met the inclusion criteria for this review.

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  Figure 3 -. Meta-analysis of studies comparing the frequency of the A1 allele of the Taq1A variant in the DRD2 gene between the obesity group (BMI ≥ 30) and the normal-weight group (BMI < 25). “Events” refers to the number of A1 alleles and “Total” refers to the number of alleles. Odds Ratio (OR) and 95% confidence intervals (CI) values are presented for fixed and random effect models.

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  Figure 4 -. Meta-analysis of studies comparing the frequency of the A1 allele of the Taq1A variant in the DRD2 gene between the group with obesity (BMI ≥ 30) and the group without obesity (BMI < 30). “OW/N” refers to the group with overweight or normal weight (without obesity), “Events” refers to the number of A1 alleles and “Total” refers to the number of alleles. Odds Ratio (OR) and 95% confidence intervals (CI) values are presented for fixed and random effect models.

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  Figure 5 -. Meta-analysis of studies comparing the genotypic means of the Taq1A variant of DRD2 in relation to the A1A1/A1A2 and A2A2 groups. “Total” refers to the number of individuals with the indicated genotypes. “Mean” refers to the mean BMI of the group. “SD” refers to the standard deviation. Standardized Mean Difference and 95% confidence intervals (CI) values are presented for random effect models.

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  Figure 6 -. Meta-analysis comparing the frequency of the long allele of the 5-HTTLPR variant in the SLC6A4 gene between individuals with overweight/obesity (BMI ≥ 25) and normal-weight individuals (BMI < 25). “Events” refers to the number of long alleles and “Total” refers to the number of alleles. Odds Ratio (OR) and 95% confidence intervals (CI) values are presented for fixed and random effect models.

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  Figure 7 -. Meta-analysis of studies comparing the genotypic means of the 5-HTTLPR variant in the SLC6A4 gene between the LL/LS and SS groups. “Total” refers to the number of individuals with the indicated genotypes. “Mean” refers to the mean BMI of the group. “SD” refers to the standard deviation. Standardized Mean Difference and 95% confidence intervals (CI) values are presented for random effect models.

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  Figure 8 -. Schematic representation of the main variants acting in the synapse. Prepared by the authors (2025). Adapted from: https://neurotorium.org/image/serotonin-and-noradrenaline-synaptic-activity-2/