You can make characters look fat by increasing some of the torso sliders, arm/leg bulk, and leg shape. It's not perfect, but I think it looks good enough, especially if you dress them in baggy clothing like robes. If you wanted to go more extreme with it, there are mods that increase the slider limits.

If the character is going to be showing much skin, you might also want to use a custom race that doesn't gain muscle definition as their stats increase. Otherwise, levels in Cooking and Science counteract muscle definition to some extent.

It is also possible to make a custom character mesh, if one knows how to use Blender. Some mod makers also take commissions.

But in game mechanics wise, no. Not the same way people can get muscular or starving bodies.

https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=2422188439&searchtext=slider