Implicating chubby → overweight
Link to implication

Reason:

Even those that are just chubby, and not obese; are still overweight.

Denied. While it may sound like it would work in name, it's not what the tags are used for. I'd recommend taking a look at the chubby wiki for a more detailed guide on how the tags are used, but here's a small summary:

• chubby - Some softness at the edges or a slight paunch. Body structure is essentially the same as a skinnier character. Not likely to be noticeable with clothes on.
• overweight - Noticeably fat or an actual gut. Body structure is essentially the same as a skinnier character but may be slightly obscured in some places.
• obese - Obviously fat, with rolls or very rounded protruding torso. Body structure is largely hidden behind fat.
• morbidly_obese - Pretty much the "hyper fat" tag, and it starts just before the "not likely to exist in real life" point (~400 lb/180 kg or so).

Long story short, chubby isn't used for characters who are overweight. There may be a possibility for renaming the tags to better reinforce usage, but as of right now this implication goes against how they are used.