BackgroundOlder adults often suffer from age- and behavior-related brain changes affecting neuronal functioning and, therefore, cognitive and motor functions. The improvement of these functions might decrease falls and improve mobility. Previous studies indicate that video game-based physical exercise, so-called exergames, or omega-3 fatty acids (FAs) improve motor and cognitive functioning through brain adaptations. The aim of this study was to assess the effects of exergame training combined with fish oil supplementation on neuronal system levels in the brain and behavioral measurements in older adults. We hypothesized that the combination would differently affect these factors compared to the sole administration of exergame.MethodsFifty-eight participants were randomly assigned to one of two groups (N = 29 each group) in a parallel, double-blind, randomized controlled trial lasting 26 weeks. The experimental group received daily fish oil, whereas the control group received daily olive oil. After 16 weeks, both groups started with an exergame training. Measurements were performed pre, during, and post intervention. Primary outcomes were recruitment curves using transcranial magnetic stimulation and response-locked potentials using electroencephalography. Secondary outcomes included executive functions and gait parameters. Blood samples were taken to control for FAs.ResultsForty-three individuals (mean age 69.4 ± 4.6 years) completed the study (Nexperimental = 22, Ncontrol = 21). The results showed no significant time × group interaction effects for any parameters. Blood samples demonstrated significant time × group interaction effects. Post-hoc tests showed a significant increase of omega-3 FAs (p < .001) and a significant decrease of omega-6 FAs (p < .001) for the experimental group.ConclusionThe combination of exergame training and fish oil did not lead to additional beneficial effects. To trigger possible effects, future studies should carefully consider study design aspects; e.g. study duration, individual nutritional supplementation dose, omega-3 FAs supplementation composition, and placebo. Furthermore, studies should consider neuroimaging methods as these might be more sensitive to assess early brain adaptations. Thus, future studies should be aware of several aspects running a combinatory study that includes omega-3 FAs according to their expected effects.Trial registrationSwiss National Clinical Trials SNCTP000001623 and ISRCTN12084831 registered 30 November 2015.