This work presents a linguistic comparison of expert-designed text-based motivational messages and peer-designed text-based motivational messages developed to influence someone’s behaviour before or during physical activity. These messages were collected in previous research and coded into the ten theory-driven categories based on the process of change, from the Transtheoretical Model (TTM). In a survey, the messages were rated on a one-item scale according to how motivating participants found them. Respondents’ stage of change was measured, and it was evaluated how this affected their preference for the motivational messages. In this research a linguistic analysis is performed using a text-analysis program called Linguistic Inquiry and Word Count (LIWC), investigating some of the differences found in the previous study on how people’s stage of change affects their preference for either peer or expert text messages. Ninety-three linguistic dimensions are considered among expert and peer messages and the ten processes of change categories. Overall, the findings proved to be very similar between peers and experts, thus, it did not help to explain, from a linguistic perspective, previous results.