The FNIH Sarcopenia Project aimed to develop clinically relevant criteria for sarcopenia, a condition characterized by low muscle mass and weakness in older adults. The project involved data from nine studies, including the Age, Gene/Environment Susceptibility-Reykjavik Study, Boston Puerto Rican Health Study, Framingham Heart Study, and others. The goal was to identify thresholds for weakness and low lean mass that are based on their relationship to strength and function. Conference attendees emphasized the importance of evaluating the influence of body mass on cutpoints. The final recommended cutpoints for weakness are grip strength <26 kg for men and <16 kg for women, and for low lean mass, appendicular lean mass adjusted for body mass index <0.789 for men and <0.512 for women. These evidence-based cutpoints, based on a large and diverse population, may help identify participants for clinical trials and should be evaluated among populations with high rates of functional limitations. The project also highlighted the need for further research to refine criteria and understand the relationship between muscle mass, strength, and function in older adults. The findings suggest that low lean mass alone is not strongly associated with function and disability, but when combined with weakness, it may be a more significant indicator. The project's recommendations emphasize the importance of using clinically relevant thresholds and adjusting for body mass when defining low lean mass. The study underscores the need for continued research to develop a robust and well-validated clinical definition of sarcopenia that can aid in the appraisal of existing literature and guide future studies.The FNIH Sarcopenia Project aimed to develop clinically relevant criteria for sarcopenia, a condition characterized by low muscle mass and weakness in older adults. The project involved data from nine studies, including the Age, Gene/Environment Susceptibility-Reykjavik Study, Boston Puerto Rican Health Study, Framingham Heart Study, and others. The goal was to identify thresholds for weakness and low lean mass that are based on their relationship to strength and function. Conference attendees emphasized the importance of evaluating the influence of body mass on cutpoints. The final recommended cutpoints for weakness are grip strength <26 kg for men and <16 kg for women, and for low lean mass, appendicular lean mass adjusted for body mass index <0.789 for men and <0.512 for women. These evidence-based cutpoints, based on a large and diverse population, may help identify participants for clinical trials and should be evaluated among populations with high rates of functional limitations. The project also highlighted the need for further research to refine criteria and understand the relationship between muscle mass, strength, and function in older adults. The findings suggest that low lean mass alone is not strongly associated with function and disability, but when combined with weakness, it may be a more significant indicator. The project's recommendations emphasize the importance of using clinically relevant thresholds and adjusting for body mass when defining low lean mass. The study underscores the need for continued research to develop a robust and well-validated clinical definition of sarcopenia that can aid in the appraisal of existing literature and guide future studies.