InstantCoffee, the way I look at it, you still have inflammatory foods in your diet. Dairy, eggs, and oats from what I recall reading in your own thread. While you may think you tolerate them my theory is that all this creates a viscous circle where your gut will never properly heal...Which I think contributes to leaky gut and nutrient malabsorption for many struggling with weight gain issues. Just my thoughts, I know that it would be inconvenient to find replacements for dairy and grains since your diet is so minimal already. But if you've been taking a good dose of L-glutamine everyday or other healing supplements and your not making any progress, then there must still be something in your diet causing an inflammatory response.
While I don't have weight gain issues myself, I'm to the point where I'm going to try an auto-immune type diet to heal leaky gut to fix my huge list of non-digestive symptoms. Removing all common inflammatory food groups while supplementing with L-glutamine, gelatin, and bone broth for a good say...6 months. That means: no legumes (soy too), grains, dairy, chocolate, eggs, nightshades, refined sugar, alcohol, seeds, nuts, dried fruit, etc. Maybe I'm wrong, maybe some of you have tried such a minimalist healing diet and got nowhere, but it seems to be as far as we can take a dietary approach. Over the past 5 years trying to get remission I've always cheated with wheat, rice, nightshades, dairy, chocolate, eggs, beans, nuts, alcohol, basically everything. I've never really dedicated a good half year to completely avoiding all these potentially inflammatory foods. I feel like I only have my self to blame for not believing in the protocol and going in circles. I guess only time will tell.
The bacteria side may be a secondary cause of leaky gut that is better treated over the long haul (a few years) with low carb diet and low FODMAP produce choices. Unless you have some rare pathogen that a doctor could help treat somehow. Short of herbal antibiotics that's all you can most likely do yourself. Maybe specific fermented probiotic and prebiotic foods can help restore a good bacteria balance, but that might not be effective until you make progress healing your gut. I have an appointment with my old GI tomorrow to see if I can be tested for SIBO and even I'm still leery of taking antibiotics.