Tags overweight, chubby, fat, obese and morbidly_obese.

Overweight is a metatag.
Wiki describes the other four as:

There's a scale of overweight-related tags:

1. chubby (plump)
2. fat (obviously overweight, but not drastically so)
3. obese (pot bellies, thighs like hams, etc.)
4. morbidly_obese (truly huge - barely or not at all capable of walking)

But overweight is currently aliased to fat and implicated by obese and morbidly_obese. So that scale is broken: if you search for fat, you get everything from fat to morbidly obese.

I'm not sure what would be the best way to fix it. Just change the descriptions or maybe unalias fat and overweight? Should fat imply overweight, instead of being aliased to it? Thoughts?