Why converting jpeg to colour profile in GIMP reduce the size so much?

Question

I have a 2MB JPEG image, and when I use the option Image > Mode > Convert to colour Profile, the size get reduced to 50KB without to much quality loss.

Could somebody explain why is the size so reduced? Am I missing some important point?

Answer 1

I observed the same long time ago while converting JPG images with Image Magic. JPEG contains information for reproduction of color components on different media. "convert to color profile" reduces this information by choosing concrete profile. This do not degrade quality. More info at ICC

Answer 2

When you reduce the number of colors within an area you reduce the amount of math needed to describe that area, which results in a smaller file size.