Although lorcaserin (APD-356, a selective 5-HT2C agonist) has been approved worldwide for treating adults with a BMI equal to or greater than 30, and adults with a BMI of 27 or greater who have at least one weight-related health condition, such as high blood pressure, type 2 diabetes, or high cholesterol [43–46], the inconsistent response to these serotonergic drugs [47] might indicate the wide variation of individual serotonergic activity and the importance of non-serotonergic pathophysiology in obesity. Here, HTR2C is linked to type 2 diabetes mellitus.