Yeah not sure if it's bro science or not, but it's often touted that doing your workout before eating will help to burn fat.
I think, technically you will be tapping into your fat reserves if you work out before breakfast because you have no food calories to burn.
But, you'll also be depleting your glycogen levels and you will be much more likely to overeat later because you're body is starved.
So it's probably right, but not massively so.
good tip - thanks