Associations of Obesity with Function and Patient-Reported Outcomes Among Rural Advanced Cancer Patients: A Cross-Sectional Analysis of the Nurse AMIE Randomized Controlled Trial

Background/Objectives: Obesity is a common comorbidity but there remains limited understanding on how higher obesity rates in rural areas may impact physical function decline and other health domains among cancer patients. This study addresses this gap by examining the association between body mass index (BMI) and physical function among a cohort of rural advanced cancer patients. Methods: This cross-sectional analysis uses baseline data from the Nurse AMIE trial (NCT04673019). Individuals were categorized as ‘normal weight’ (BMI ≤ 25 kg/m²), ‘overweight’ (BMI > 25 to 30 kg/m²), and ‘obese’ (BMI > 30 kg/m²). Objective physical function was measured by the Short Physical Performance Battery (SPPB) and subjective physical function and health domains were measured using surveys (PROMIS; SF-36). Results: Of 348 patients included, 88 (25.3%) were classified as ‘normal weight’, 107 (30.7%) as ‘overweight’, and 153 (44.0%) as ‘obese’. Average age was 64.8 years (SD = 12.2), 46% (n = 160) were female, 95% were white (n = 331), and 52% (n = 182) were Stage 4. Total SPPB scores revealed poorer functioning with higher BMI (M ± SD: BMI ≤ 25 kg/m²: 9.1 ± 2.3; BMI > 25–30 kg/m²: 8.3 ± 3.1; BMI > 30 kg/m²: 8.1 ± 2.8; p = 0.04). Similarly, scores from the SF-36 revealed subjective physical function was lower with higher BMI (BMI ≤ 25 kg/m²: 57.9 ± 29.1; BMI > 25–30 kg/m²: 53.7 ± 28.0; BMI > 30 kg/m²: 47.6 ± 27.6; p = 0.004). Participants reported lower levels of energy and greater fatigue with higher BMI (BMI ≤ 25 kg/m²: 49.8 ± 26.1; BMI > 25–30 kg/m²: 45.1 ± 24.6; BMI > 30 kg/m²: 40.7 ± 22.6; p = 0.01). Conclusions: Higher BMI is associated with poorer physical function and increased fatigue among rural advanced cancer patients, highlighting the need for supportive care related to physical function in this at-risk group.