You're asking the right question. I'm not an expert, but from what I've read, there is 0 evidence that allergens create a gut. What there is evidence for is that food intolerance (big difference) can create bloating, and the bloating can get pretty big, ala gut. However, if someone has serious, long-term bloating due to a consistent diet of a food that their body has an intolerance to, they almost certainly have stomach pains and other related symptoms. We're talking about bloating from gas. So the idea that food intolerance creates a gut doesn't explain most guts. It probably doesn't explain the OP's gut.
Elimination diets probably work because when you cycle through major food groups like grains or dairy, you're probably just eating fewer calories. So people will spend years thinking they have a dairy intolerance that they don't have (sad), when they could have eaten grains no problem and just cut calories. Or they might have a slight dairy intolerance (get a little gas), and then chalk up their big weight loss on the idea that their intolerance is huge.
OP hasn't responded to me, but it seems like he is eating at maintenance or above, and he's just doing cardio, which isn't getting him where he wants to be.