Altered asymmetry of amygdala volume mediates food addiction and weight gain.

Background: Food addiction and an impulsive personality can increase overeating, which can lead to weight gain. The amygdala and nucleus accumbens (NAcc) are critical for regulating obesogenic behaviour. However, whether the amygdala or the NAcc acts as the neural basis for the regulation of food addiction, impulsive personality, and body weight remains unclear.

Methods: We examined the differences in the volume of the amygdala and NAcc, especially the lateralization index (LI), between 33 obese participants and 39 age- and sex-matched healthy controls. The associations of the LI of each brain region with clinical variables and body mass index (BMI) were identified using network analysis. Finally, we explored the relationships among the LIs of brain regions, impulsive personality, food addiction, and BMI through a multiple chain mediation model.

Results: We observed a significant decrease in the LI of the amygdala in the obese group compared with the healthy group (F = 20.276, p < 0.001), which indicates that the right amygdala was larger than the left amygdala in the obese group. Network analysis revealed that the LI of the amygdala was very closely associated with nonplanning impulsivity, food addiction and BMI. The results of the mediation analysis indicated that increased nonplanning impulsiveness could lead to weight gain through increased food addiction (β = 0.069, SE = 0.043, 95% CI [0.014, 0.184]). Moreover, in this symptom chain, the LI of the amygdala can mediate the relationship between food addiction and BMI (β = 0.018, SE = 0.014, 95% CI [0.002, 0.061]).

Conclusion: Our observations indicate a substantial reduction in the LI of the amygdala among individuals with obesity, suggesting a structural predisposition. The findings reveal a potential neural mechanism that can help explain the interplay between impulsivity, food addiction, and obesity.