A better understanding of the motives underlying the adoption of sustainable and healthy diets is needed for designing more effective policies. The aim of the study was to examine how eating motives were associated with self-reported changes in the consumption of beef, beans, and soy products, i.e., changes related to reducing animal and increasing plant proteins. The study analysed a survey of an adult population living in Finland (N = 1048). The eating motives were measured with the Eating Motivation Survey (TEMS), which distinguishes between 15 eating motives. Six clusters of consumers based on self-reported changes in food choices were identified with latent class analysis (LCA). Four clusters had established food consumption patterns ("Beef only", "Beef and beans", "Beef, beans, and soy products", and "No beef"), one was undergoing a change, and one had attempted a change earlier. ANOVA with planned contrasts revealed that the motives relating to natural concerns, health, and weight control were higher, and convenience and price lower, among those who had an established diet including beans and soy products, as compared to those who consumed only beef. Those undergoing a dietary change expressed a higher endorsement of natural concerns as well as health, sociability, social image, and price motives than those with an established diet including beans and soy products. The results suggest that eating motives play an important role in changing towards more sustainable food consumption patterns in which meat/beef is replaced with plant proteins.