Obesity as a disease remains poorly understood by key stakeholders. Here, in people living with severe obesity, perceptions and beliefs relating to obesity as a disease and obesity causality were examined. Semi-structured interviews were conducted in a tertiary care obesity clinic. 23 people with obesity (10 males, 13 females) volunteered. An overall agreement that obesity is a disease was present. Perceptions related to why obesity is and is not a disease were diverse: Lack of control and addiction, biological determinism, and personal responsibility. For weight loss maintenance, the perceptions and beliefs were heterogeneous with biological factors not considered a determinant of success. Instead, exercise, support, and willpower were described as associated with success. Barriers related to remaining in a weight-reduced state included the following: Emotional eating, sustainability of diet, occupational impact, and defeatism due to misaligned expectation and outcome. In conclusion, people living with obesity tend to agree obesity is a disease yet an incomplete understanding of the disease is present.