Background: Massive Open Online Courses (MOOCs) can engage large numbers of learners. Understanding motivations for enrolling and elements that engage learners may help meet learner needs. This study explored motivations, intentions, recruitment methods and course acceptability of learners enrolled in 'The Science of Weight Loss: Dispelling diet myths' (SWL101X) MOOC on EdX. Design and setting: Cross-sectional analysis included 29,666 learners from 180+ countries. Methods: Learners provided demographic data, while 8,454 learners provided optional pre-course data and 987 provided post-course data. The pre-course survey examined learners' motivations and intentions and recruitment method, and the post-course survey examined acceptability of course content. Descriptive statistics were reported as frequencies and percentages or medians (interquartile range)/means (standard deviation). Results: Learners (61% women, 51% aged between 25 and 44 years) enrolled in the MOOCs mainly to increase their nutrition knowledge (46%) and/or lose weight (62%). Most (61%) were recruited through EdX platforms (website, newsletters and blog). Course components were well received by the majority who completed the post-course survey. Conclusion: The SWL101X MOOC successfully delivered nutrition education. Future courses could consider trialling the text, videos and interactive features to further engage learners. Short, informal 'talking head' video content may facilitate engagement. Future courses should also ensure the inclusion of the most recent dietary practices for health, and the management of obesity as a chronic disease, as some of the content used in the course in this study does not represent current and/or best practice. The greater use of social media may enhance learner enrolment.