The co-occurrence of obesity with cancer-related fatigue and their impact on physical function among breast cancer survivors

Purpose To evaluate the associations of obesity and cancer-related fatigue (CRF) among breast cancer survivors, and the impact of their co-occurrence on physical function.Methods In a nationwide randomized clinical trial, we assessed body mass index (BMI; kg/m2), CRF via the Brief Fatigue Inventory (BFI), and physical function via hand grip dynamometry (muscular) and 6-minute walk test (cardiorespiratory) among breast cancer survivors at baseline.Results Among 456 participants with a breast cancer diagnosis (stage I–IIIC, mean age 55.9 years, 23.5 months post first-treatment, 86% white), 43.9% have obesity (BMI ≥ 30 kg/m2), and 32.7% have overweight (BMI 25–29.9 kg/m2). Compared to those with a normal weight, survivors with obesity are more than twice as likely to experience moderate-severe CRF (BFI total score ≥ 4; OR [95%CI] = 2.21 [1.35–3.63]). Survivors with co-occurring overweight/obesity and moderate-severe CRF have significantly worse cardiorespiratory function than those with either condition alone.Discussion Overweight/obesity and CRF are highly prevalent among breast cancer survivors. Survivors with obesity experience worse CRF compared to those with normal weight. Survivors with co-occurring overweight/obesity and severe CRF experience worse cardiorespiratory function, and this persists post-diagnosis. Given the long-term detrimental impact of these conditions on QOL and survival, these findings underscore the need for targeted interventions.