This advice-column-style blog for SLPs was authored by Pam Marshalla from 2006 to 2015, the archives of which can be explored here. Use the extensive keywords list found in the right-hand column (on mobile: at the bottom of the page) to browse specific topics, or use the search feature to locate specific words or phrases throughout the entire blog.
Q: My daughter has a lateral lisp and obesity. The SLP cannot seem to get her to make the correct sounds. Can obesity interfere with learning these sounds?
I have never faced this situation with any client. However, from what I know about tongue function and the lisps, I do not see how obesity might interfere with learning correct tongue position for S, Z, Sh, Zh, Ch, or J.
Perhaps your SLP does not know how to fix a lateral lisp. This is very common today. You may have to seek additional help from another SLP.