With the application of any control the model will slow slightly. With most normal cg positions and trim setups the airplane will attempt to regain speed by dropping the nose. It is not really an 'elevator' effect as you don't have to move the elevator for this to happen. Take a model, any model, out to the field, get it dong a bit of 'S&L' all by itself, then apply any control and hold it. Note that, if you hold it long enough, the model will impact the ground. You can do this with either aileron or rudder, without touching the elevator at all. All to do with the lift being angled off with the attitude of the model, and not being allowed to correct because the continued application of the control.
Evan.