ABSTRACT Accounting for more than 60% of cancer survivors, older (≥65 years) cancer survivors, have a 2- to 5-fold risk of physical function impairment, compared to cancer-free controls. Physical function impairment has multiple deleterious health effects including poor health-related quality of life (HRQoL), multi-morbidity, increased falls, and all-cause mortality. One strategy to improve physical function is dietary and resistance training interventions, which improve muscle strength and mass by stimulating muscle protein synthesis. However, there are no synchronous, online diet and exercise interventions for older cancer survivors, a group at high risk for functional limitations. Thus, the E-PROOF (E-intervention for Protein Intake and Resistance Training to Optimize Function) study will examine the feasibility, acceptability, and preliminary efficacy of a 12-week randomized controlled trial of an online, tailored nutritional and resistance training education and counseling intervention to improve physical function and associated health outcomes (muscle strength, HRQoL, self-efficacy, and weight management). We postulate that, compared to the control group, intervention participants would experience statistically significant, clinically meaningful improvements in physical function and associated health outcomes following the 12-week diet and resistance training intervention. To achieve our objective, we will: 1) Determine the feasibility and acceptability of implementing an online dietary and resistance training intervention among 70 older cancer survivors; and; 2) Examine the preliminary efficacy of an online dietary and resistance training intervention to improve physical function and associated outcomes among 70 older cancer survivors who participated in a 12- week intervention. In this pilot randomized controlled trial, participants will be randomized to one of two groups: one experimental (online counseling by a registered dietitian and exercise scientist, menus, educational materials on protein, healthy diet, resistance training) and one control (general survivorship education). We will examine the intervention effects on physical function, muscle strength, HRQoL, self-efficacy, weight, and waist circumference during a 12-week period between the experimental and control groups. We will conduct a 3-month follow-up to assess physical function, muscle strength, and HRQoL. The feasibility of conducting an online diet and resistance training intervention in older cancer survivors will be determined by the study accrual, retention, and adherence rates. This study will inform the development of a R01 scale randomized controlled trial to evaluate the effectiveness of a protein-focused meal delivery program and resistance exercise regimen on risk for functional impairment and sarcopenia among older cancer survivors. The study goals respond to the NIA and NCI missions to address the research gaps in older cancer survivors and help them lead longe...