This could be because the body increases insulin secretion in anticipation that sugar will appear in the blood. When this doesn’t happen, blood sugar drops and hunger increases. Whether this chain of events regularly takes place is somewhat unclear. Something odd happened when I tested Pepsi Max though, and there are well-designed studies showing increased insulin when using artificial sweeteners.
Mason, A. E., Epel, E. S., Aschbacher, K., Lustig, R. H., Acree, M., Kristeller, J., … Daubenmier, J. (2016, May 1). Reduced reward-driven eating accounts for the impact of a mindfulness-based diet and exercise intervention on weight loss: Data from the SHINE randomized controlled trial. Appetite , 100, 86–93. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4799744/