Gigantor

Here is a question that I have been pondering for a bit....If the Accord can weigh around 3200 pounds, get good crash rating and because of that weight get improved fuel economy, why does the Epsilon I platform have to weigh about 3600 pounds? How much will the Ep II platform weigh? A power train can only be so efficient, it just seems that GMs platforms are really on the heavy side. Am I nut?