Background: Prospectively registering randomised controlled trials (RCTs) is an integral part of proper trial conduct and is enforced for trials of regulated interventions including drugs, biologics and devices. However, the registration of trials of non-regulated interventions including diets, exercise, surgery and therapies has received less attention.

Objectives: In the current study, we performed a search of RCTs of non-regulated interventions to assess: 1) journal prospective trial registration policies; 2) the proportion of prospectively registered RCTs; and, 3) the adequacy of outcome registration.

Methods: The search strategy included all journals listed in the 2014 Thomson Reuters Journal Science Citation Index - Expanded categories of behavioural sciences, nursing, nutrition & dietetics, psychology, rehabilitation and surgery. We searched daily for RCTs of non-regulated interventions that appeared in PubMed from 18 March to 17 September 2016. Information on journal-registration requirements, trial registration and outcome definition was extracted.

Results: We reviewed 953 eligible trials published in 254 journals. Among the 254 journals, 43 (16.9%) journals required prospective registration of published trials. Of 953 included trials, only 189 (19.8%) were registered prospectively. Only 60 of the 454 registered trials (13.2%) were registered pre-enrolment, clearly defined a primary outcome variable and time point, and were considered as adequately registered. Of the 60 articles reporting on trials with adequately registered outcomes, 35 (58.3%) articles reported outcomes analyses in a manner that was consistent with registered outcomes.

Conclusion: The rate of registration of RCTs of non-regulated interventions, the rate of registration and the adequacy of outcome definition is less than ideal. Greater efforts beyond journal policies to increase prospective trial registration practices and adequate reporting of outcomes are warranted.