Purpose <p>The study aimed to describe the socio-demographic determinants and personal motivations that influence the practice of physical activity in the Spanish population, and the relationships between physical activity and nutritional and lifestyle habits.</p> Methods <p>This was a cross-sectional survey with the self-administered NutSo-HH Scale mostly disseminated on social media platforms, using the non-probabilistic snowball method. Data was collected from August 2020 to November 2021 using an online form.</p> Results <p>The sample included 22,181 adult residents in Spain, weekly engaged on average in 158.2&#xa0;min of physical activity. Young people were more active in physical activity (41.8%) than middle-aged individuals (34.5%). Men (56.2%) participated in physical activity more than women (33.6%), and those with basic education were less active (38.6%) compared to those with higher education (31.7%). Economic level, size of city of residence, and diet had little impact on physical activity. Higher physical activity was associated with less consumption of unhealthy foods, more water consumption, and better self-perceived health. The main barriers to physical activity were lack of motivation (52.4%) and lack of time (26.14%), while financial problems were rarely a factor (1.21%).</p> Conclusions <p>Socio-demographic factors, personal motivations and time management must be addressed to promote physical activity in Spain. Public health initiatives and work-family reconciliation policies should consider these factors to encourage a more active and healthy population.</p>