Methods of utilizing quantitative magnetic resonance (QMR) to non-invasively determine and quantify body fluid dynamics [e.g., extracellular water and total water levels] and body compositions (e.g., lean muscle mass and fat mass levels). These levels or changes therein are used as biomarkers to diagnose, prognose, tailor and monitor treatment for conditions that cause or caused by ECW retention (edema), lean muscle mass loss (sarcopenia), and/or fat loss (cachexia), including heart failure (HF) and HF-associated and HF-non-associated edema/sarcopenia/cachexia, kidney disease, liver disease, and other HF complications. Body fluid dynamics and body compositions measurements obtained from QMR technology are used as biomarkers to help a physician's assessment to determine the prognosis and personalized treatment strategies that are tailored for individual patients with heart dysfunction and/or HF, HF-associated conditions, and/or other conditions that cause or caused by edema, sarcopenia, and/or cachexia.