Body mass index is an important element influencing surgical outcomes after total hip arthroplasty. This review analyses how body mass index influences perioperative complications, infection rates, implant survival and functional results in patients undergoing this procedure. A literature review of the past decade was carried out using PubMed, Scopus and Web of Science, focusing on studies published between 2020 and 2026. Studies involving humans that examined the relationship between body mass index and outcomes of total hip arthroplasty were included if they reported perioperative complications, infections, revision rates, or patient-reported outcome measures. The evidence indicates that a higher body mass index is associated with an increased risk of wound complications, periprosthetic joint infection and the need for revision surgery. It is also associated with a lower possibility of achieving minimal clinically important differences in functional scores. The relationship follows a U-shaped pattern showing that, compared with normal weight, obesity and underweight status are associated with increased risk. Proposed mechanisms include technical surgical challenges, altered immune function, compromised wound healing and greater mechanical stress on implants. Preoperative optimization strategies consist of nonsurgical weight loss and bariatric surgery. They are promising but require more investigation. New pharmacological approaches using glucagon-like peptide-1 receptor agonists are a useful contribution to perioperative care. Future research should focus on finding biomarkers of obesity-related risk and on developing individualized strategies to improve outcomes across the body mass index spectrum.