Camellia oil is traditionally regarded as a health-promoting dietary oil in Asian populations, particularly for its potential benefits to metabolic balance and gastrointestinal function. Its fatty acid profile is similar to olive oil, which has been shown to improve lipid metabolism and support weight regulation. However, scientific evidence regarding the clinical effects of camellia oil remains limited.This study aimed to investigate the impact of long-term camellia oil consumption on body mass index (BMI) in adults.This prospective self-controlled study initially enrolled 36 participants aged 20 to 75 years who agreed to consume camellia oil daily as part of their regular diet. Subjects were instructed to use camellia oil for cooking while maintaining their usual dietary patterns and lifestyle, without adopting other weight-loss interventions. After six months, two participants were excluded due to incomplete follow-up, leaving 34 individuals for final analysis. BMI was measured at baseline and at the end of the six-month intervention. A paired t-test was used to compare changes in BMI before and after camellia oil consumption. The study was approved by the Institutional Review Board of Tungs’ Taichung MetroHarbor Hospital (IRB No. 113039), and all procedures complied with the principles of the Declaration of Helsinki.The mean baseline BMI of the 34 participants was 24.25 ± 6.15 kg/m². After 6 months of continuous camellia oil consumption, BMI decreased to 23.15 ± 4.15 kg/m², reflecting an average reduction of 1.10 kg/m²; however, this change did not reach statistical significance (p = 0.075). Although a downward trend was observed, no serious adverse events were reported, and overall adherence to the dietary protocol was satisfactory.Six months of camellia oil consumption was associated with a slight reduction in BMI; however, this change did not reach statistical significance (p = 0.075). Furthermore, the flavour of camellia oil might affect appetite, which, in turn, influences weight.While a downward trend was observed, the effect remains inconclusive and should be interpreted cautiously. Larger, well-designed randomized controlled trials are required to determine whether camellia oil exerts a clinically meaningful impact on body weight regulation.