Meeting physical activity guidelines in conjunction with higher protein intake: associations with appendicular lean soft tissue index in middle aged adults with cancer

Abstract Background Loss of muscle mass is a common concern among patients with cancer. The aim of this study was to examine whether meeting the World Health Organization physical activity guidelines in combination with a higher vs. lower than the recommended daily allowance (RDA) protein intake is associated with greater appendicular lean soft tissue index (ALSTI) in adults aged 40–59 years with cancer from the National Health and Nutrition Examination Survey. Methods Participants were categorized by physical activity levels (moderate ≥ 150 min/week or vigorous ≥ 75 min/week) and protein intake (> 0.8 vs. ≤ 0.8 g/kg/day) assessed via two interviewer-administered 24-h dietary recalls. ALSTI was calculated using dual-energy X-ray absorptiometry (kg/m 2 ). Linear regression models estimated associations, adjusting for demographic, clinical, and dietary covariates. Results Among 169 participants (mean age 51.0 ± 5.6 years; 69% women, mean ALSTI 7.74 ± 1.66 kg/m 2 ), those meeting vigorous or moderate physical activity guidelines with higher protein intake did not show a significant association with ALSTI in the fully adjusted models (vigorous: β = 0.08, standard error (SE) 0.12, p = 0.53; moderate: β = -0.05, SE 0.15, p = 0.76). However, a significantly positive link was found in those meeting both vigorous and moderate physical activity (β = 0.40, b SE 0.02, p < 0.01). Conclusions Meeting vigorous or moderate physical activity guidelines in combination with higher vs. lower protein intake was not associated with ALSTI in adults with cancer. However, meeting both was positively linked to ALSTI. Longitudinal and interventional studies using objective measures and longitudinal designs are needed to clarify the role of physical activity with adequate protein intake in preserving muscle health in this clinical population.