Background The aim of this study is to evaluate the effect of bite raisers on patients' body mass index (BMI), nutrient intake, periodontal status, and pain experienced during orthodontic treatment. Material and Methods This cohort study included 44 patients aged 18 to 35 years old; undergoing fixed orthodontic treatment. Patients of the intervention group received a composite resin bite raiser (3M Espe, St. Paul, USA) over their first mandibular molars along with fixed orthodontic appliances (slot 0.022 × 0.030", 3M Unitek, Monrovia, Calif), while the control group only received a fixed orthodontic appliance. Pain levels using the visual analog scale (VAS), dietary intake (calories, proteins, carbohydrate, and fat intake), body mass index (BMI), tooth mobility, bleeding on probing (BOP), and pocket depth (PD) were assessed for all patients in the first three months after fixed orthodontic appliance placement. The data were analyzed using SPSS software version 22.0 (IBM Corp, Armonk, NY, USA) at a significance level of 0.05. Results The pain had an increasing and then decreasing significant trend during the study for all patients (P<0.001). Calory intake also had an increasing and then decreasing significant trend for all participants (P=0.007). The consumption of carbohydrates and BMI significantly decreased during the study in both groups of patients (P<0.01) and tooth mobility, BOP, and PD significantly increased for all participants (P<0.001). No significant differences were observed between the intervention and control groups in terms of the above-mentioned variables. Conclusion The application of bite raiser does not influence patients' pain, dietary intake, BMI, and periodontal status. However, fixed orthodontic appliances affect patients' calorie and carbohydrate intake, patients' BMI, and periodontal indexes including tooth mobility, BOP, and PD.