First off, I am just a hobbyist, I can't possibly tell you about the clinical facts you are asking for. And I too would like to see a clinical study on the subject, but I have not found one available.
I think where some of the confusion lays is what is the definition of bloat. There is a high percentage of infected fish that die long before they literally bloat. In the hobby bloat is more of a catch all term. When one starts loosing fish for some unknown reason they say it is bloat. To me bloat is really a breakdown of the immune system that is caused by stress. This stress can cause all sorts of problems, but the bottom line seems to be in the incapacity of being able to fight off one or several problems that range from bacterial infections, parasites/pathogens/flagellate and digestive issues.
Aggression, water conditions and diet seem to lead the list for causes. While some are physical, aggression can certainly be, mental. In the wild the abused fish can swim away, in our tanks they canâ€™t. And it is not just subdominant fish that can stress out from this aggression, but there is also pressure on dominant fish to keep his status. Water conditions should be a no brainer, but poor water conditions can make fish more aggressive, as well as higher temperatures.
Diet is one thing that we have control over, but yet we cannot control ourselves. Hobbyists consistently over feed their fish, it is well known that our tank specimens usually exceed the average size in the wild, and live longer. Fish do not digest warm-blooded animal fats properly and the fat ends up in the fishâ€™s liver, and after time this kills them off too. Are we confusing this with bloat? Hobbyists are not dissecting their fish when they die, so we donâ€™t know if it is fatty liver disease, a parasite bloom or a blockage in the digestive system. Feeding sparingly and feeding high fiber foods, seems to decrease problems with bloat. It also depends on many other things, like the length of digestive system, and what the fish actually eats in the wild. Although mbuna are classified as vegetarians, many of them eat insects, crustaceans, plankton and even fry of other fish.
The recommend medication for bloat is Clout, which is for parasites, and so why does it work so well on bloat? I know that it doesnâ€™t really make sense, but it is the only thing I have found to work. Compounded with the fact that there are just too many variables in uncontrolled environments. Bloat has been around for years, and it is still controversial and will remain to be, as there is no black and white definition of it.
I can only share my experiences and experiences of the many hobbyists that I come in contact with. After many years of working with Cichlids, and certainly killing my share, I really believe that preventative maintenance is answer to curbing bloat. You have to know the species you are working with, as they are all a little bit different and provide the ideal conditions. I donâ€™t think bloat is just diet related, it also has to do with many other factors related to being in an aquarium, the biggest of which is stress.
Hope this helps some!