An online system receives a request for a video to be presented by the online system to a target user. The online system determines whether to insert secondary content into the video. For such a determination, the online system identifies a position in the video for inserting secondary content. Further, the online system determines a loss score and a gain score. The loss score measures a loss of interaction by the target user if the secondary content were inserted. The gain score includes a monetary compensation to be received by the online system for inserting the secondary content at the identified position. The online system compares the loss score and the gain score. Based on the gain score offsetting the loss score, the online systems modifies the video by inserting the secondary content at the identified position and provides the modified video for display to the target user.