Hank, or Dr. Smith, is the novel’s primary antagonist and the architect of Emmett’s suffering. As a character, he is round and static, driven by a consistent and deeply rooted obsession with physical purity and control. Hank’s abuse of Emmett during his childhood is framed as a misguided attempt to impose “healthy habits,” a twisted form of care rooted in his own upbringing by an abusive, military-veteran father. His actions, particularly the traumatic incident where he force-fed Emmett his own vomit, established a direct link between food, shame, and violence in Emmett’s mind. Hank’s personal history of torment makes his later role as the founder of a weight-loss company a chilling continuation of his pathology.

After being fired from a research institute for unethical experiments, Hank changed his name to Cecil H. Smith and founded Monstera BioSciences, a company dedicated to eradicating obesity. This reinvention allowed him to pursue his obsessive quest for a “miracle solution” on a grand scale. He developed Obexity, a drug inspired by the story of a historical cannibal, Sir Percival Blount, suggesting that he was aware of its potential for monstrous side effects from the beginning. He embodies The Exploitative Nature of the Weight-Loss Industry, viewing the desperation of people with obesity as a scientific problem to be solved through extreme, and ultimately dangerous, means. His selection of his estranged stepson, Emmett, for the clinical trial is a deeply perverse act of “charity,” demonstrating his continued desire to control and reshape Emmett’s body. Hank’s survival at the end of the novel and his appointment as director of the FDA’s Center for Drug Evaluation and Research, where he approves his own deadly product, is the ultimate cynical statement on the corrupt and self-serving nature of the systems that profit from body shame.

Dr. Saito is an antagonist and a critical foil to Emmett, a round and static character whose motivations add a layer of complexity to the novel’s exploration of retribution. As Monstera’s director of product development, she is the charismatic public face of the company. Like Emmett, she has personal experience with the trauma of body shaming, having been marginalized as a woman of Japanese descent living with obesity. However, where Emmett craves societal acceptance, Dr. Saito craves vengeance. She confesses to Emmett that her goal is to get even with a society that dehumanized her: “Obexity isn’t just about getting thin; it’s about getting even” (297).

Dr. Saito is a brilliant and manipulative scientist who secretly steers Obexity’s development to enhance, rather than eliminate, its violent side effects. She views the drug as a weapon, a way to turn the victims of fatphobia into literal monsters who will enact her revenge for her. She orchestrates a massive cover-up, using genetically modified coyotes and a compromised police chief to hide the murders committed by trial participants. Her calculated deception of both Emmett and her boss, Dr. Smith, reveals her as a Machiavellian figure who is just as controlling and abusive as Hank, though her methods are more subtle. By exploiting Emmett’s pain and shared history, she shows a darker path of empowerment, one that seeks not to heal trauma but to weaponize it, ultimately perpetuating a cycle of violence.

Lizette is Emmett’s best friend, serving as his main ally or sidekick. As a round and static character, she is the story’s moral and emotional center, representing an alternative to the self-hatred that Emmett feels. Lizette is a proud, confident woman who embraces her body and refuses to be shamed by societal standards. She channels her energy into her plus-size clothing brand, GORDITA, which celebrates bodies with obesity rather than seeking to change them. Her worldview directly challenges the premise of The Social Currency of Appearances, as she has built a successful and fulfilling life without conforming to other people’s beauty ideals.

Throughout the novel, Lizette is Emmett’s most steadfast source of unconditional love and support. She is his confidante and protector, accompanying him to the initial Monstera information session to ensure his safety and remaining loyal even after learning about his horrific crimes. While she’s horrified by his actions, she correctly identifies the drug as the true source of the monstrosity, telling him, “Nothing’s wrong with you […] It’s the drug” (228). However, her loyalty doesn’t prevent her from challenging him. She’s critical of the superficial validation he receives online and is hurt when his newfound thinness fosters a judgmental attitude toward her. Lizette represents the kind of self-acceptance that Emmett finds it challenging to embody due to his deep-seated trauma. Her unwavering friendship highlights the tragedy of his failure to see his own worth beyond his weight.

Aaron is a key secondary character who functions as Emmett’s romantic interest. A flat and static character, Aaron has been the object of Emmett’s affection since graduate school and is the living embodiment of The Social Currency of Appearances. He shows no romantic interest in Emmett until Emmett loses a significant amount of weight, at which point he actively pursues a relationship. His attraction is revealed to be entirely superficial and conditional, as he’s immediately disgusted upon discovering the loose skin on Emmett’s stomach, a natural consequence of rapid weight loss. He is unable to see past this physical imperfection, which he views as a reminder of Emmett’s former body.

Aaron’s ultimate rejection of Emmett is both cruel and hypocritical. He shames Emmett for using a weight-loss drug, accusing him of dishonesty, and finally calls him a “monster.” This verbal attack, coming from the person whose approval Emmett craved most, acts as the final trigger for Emmett’s rage, leading directly to Aaron’s violent death. Aaron’s character illustrates the precariousness of conditional acceptance and is a powerful symbol of a society that rewards conformity to beauty standards but offers no compassion for the messy, imperfect realities of human bodies.