GD2 gif resizing problem

I'm trying to resize GIF images and up with very large files For example: Original width = 720 New width = 980 Original height = 1008 New height = 1274 Original filesize = 80kb After resizing = 235kb Based on the area increase; I'd expect the file size to about double, not be 4x as large. $src_img = imagecreatefromgif($filename); $dest_img = imagecreatetruecolor($new_width, $new_height); imagecopyresampled($dest_img, $src_img, 0, 0, 0, 0, $new_width, $new_height, $org_width, $org_height); imagegif($dest_img, $filename); I tried using imagetruecolortopalette() and it helped a little; but screwed up the image quality. Can anyone explain or have a solution? Thanks....