Riffing off of that creatively is where the GAPS woo originates.
I am not aware of much devoted specifically to combat this particular woo.
Many of the symptoms of leaky gut are supposedly pretty similar to the ones I have, including seemingly unrelated problems like arthritis.
Most of what the leaky gut devotees do is not bad stuff in any case, even if it won't cure all that ails you.
So while it's not completely proven, I think there's a reasonable theory at work here.
But the new movement has gone far beyond the original work.
Here's a fun trashing of the idea with the usual comment as a response."Leaky gut" is indeed real and certainly could play a role in autoimmunity: Is it really hard to believe that intact foreign proteins entering the peripheral circulation and eliciting an immune response could contribute to autoimmunity? The Internet use of it as a cause of all diseases that they care to include is quackery.
So is the notion that the immune system resides in the gut.
You cannot get around Internet stupidity by noting the grain of truth they they build their sand castles around.