Intestinal permeability however and bacterial translocation, is what KDM diagnosed me with. These are just the correct terms. When KDM uses the term Leaky gut, he most likely is saying that as a way for a lay person to undertsand intestinal permeability. If you see this research on Liver function, you can see intestinal permeability and bacterial translocation is a validated diagnosis, which is believed to cause all manner of health issues
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4451427/
It was discovered not that long ago, that Zonulin had a role to play in intestinal permeability - being increased in people who show problems with the tight junctions in the gut
https://www.ncbi.nlm.nih.gov/pubmed/21248165
In turn we can see that KDM uses a stool test to check for levels of Zonulin, which may indicate intestinal permeability
I had the above test done and it showed high levels of IGM against a variety of gut microbes in my blood stream. Bcaterial translocation is a known medical issue.
http://www.redlabs.be/ida
Do note that 'leaky gut' is used in quotation marks to show its colloquial use for intestinal permeability etc.