OBJECTIVE: To categorize the research topics covered by a sample of randomized controlled trials (RCT) included in systematic reviews of nutrition interventions to address obesity; to describe their funding sources; and to explore the association between funding sources and nutrition research topics. DESIGN: Cross-sectional study. SUBJECTS: RCT included in Cochrane Reviews of nutrition interventions to address obesity and/or overweight. RESULTS: Two hundred and thirteen RCT from seventeen Cochrane Reviews were included. Funding source and authors' conflicts of interest were disclosed in 82·6 and 29·6 % of the studies, respectively. RCT were more likely to test an intervention to manipulate nutrients in the context of reduced energy intake (44·2 % of studies) than food-level (11·3 %) and dietary pattern-level (0·9 %) interventions. Most of the food industry-sponsored studies focused on interventions involving manipulations of specific nutrients (66·7 %). Only 33·1 % of the industry-funded studies addressed dietary behaviours compared with 66·9 % of the non-industry-funded ones (P=0·002). The level of food processing was poorly considered across all funding sources. CONCLUSIONS: The predominance of RCT examining nutrient-specific questions could limit the public health relevance of rigorous evidence available for systematic reviews and dietary guidelines.