In mice a high fat lab chow does increase obesity/symptoms of metabolic disorder because mice are built to naturally consume a low fat diet. A mistake some researchers may make is to assume (due to decades of inappropriate demonizing of fat in human diet) that harms of high fat chow to mice will equally apply to high fat consumption in humans. Not so. Humans respond very differently to dietary fat than do mice. In a sense kind of like saying broccoli would do great harm to humans because it makes lions (obligate carnivore) sick. Or that because force feeding animal cholesterol to totally herbivore rabbits messes them up (yeah, that study was done) therefore humans (or maybe lions, tigers and bears, oh my!) shouldn't eat cholesterol either? So okay, after accounting for the different means needed to produce metabolic disorder/obesity in differing species (human+high grain "mouse" food=obesity?), the effect of fiber on that metabolic disorder is a curiosity, that is, will humans also benefit? And are we talking adding a refined fiber product to a highly refined food-like human diet suspiciously reminiscent of better tasting lab chow, sort of like they did with these little mouse guys? Who knows, could be some benefit there for humans adding commercial fiber-in-a-bottle to refined typical diet. Really, there could be.
Although I'll personally pass and just keep eating a whole foods real human diet with fiber that comes along for the ride.