I have problems with this too. One thing that seems to work is that I try drinking 8 oz water before eating anything. It may not stop me completely but it does slow me down.

I eat in this order if I can, to slow myself down: water, then healthy crap like veggies, then protein, then carbs, then I save the refined sugars and less healthy stuff for last.

Not perfect, but it is like putting your foot to the floor on a faulty break.