Does over-exercising cause the same metabolic reaction as starvation?

Yes. Both burn fat and protein, after using what little glycogen in the body. This is not lactic acidosis, but metabolic acidosis, and occurs also in people who on low carbohysdrate diets. This a naturally occuring event. Lactic acidosis occurs when muscle, because of too strenuous activity, so Lactic Acid accumulates and causes muscle fatigue/burn. Lactic acid is reutilized and tunred into glucose.