Depending on which version you are using, the lists may vary. I am still holding on to SE since there is the largest amount of mod compatibilities. There are a number of mod combinations that achieve similar results but here is my current “Weight-Gaming-esque” set up that may get you the results you want:
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Winterweight at Skyrim Special Edition Nexus - Mods and Community - Provides real-time body morphs for eating/drinking. You apply the weight sliders yourself so you can set the max weight to immense proportions if you want. It also has penalties for being overweight (like stamina reduction) but I don’t know if you can truly become immobile. You can also set it up so followers eat food that you drop from your inventory, adding to the fun.
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WeightMorphs SE at Skyrim Special Edition Nexus - Mods and Community - Another dynamic weight morphing mod. I currently am not running this one (Winterweight and Devourment cover my needs), but you can set this one up to reduce your stamina and movement speed as you gain weight. If you play around with the morph settings, you should be able to have both mods running and let one do the primary morphing while you get your desire penalties.
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SunHelm Survival and needs at Skyrim Special Edition Nexus - Mods and Community - Survival mod that is fairly customizable and has penalties for not eating/driking/sleeping.You can make your character ravenous essentially, requiring you to eat a lot, thus gaining more weight faster if you set it up that way in Winterweight.
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Devourment Refactor - Comprehensive vore mod. There is a new AE version as well, just search the forum for the link. This also has a weight morph function in the MCM and is compatible with Winterweight. I disable them because the combo can make your character grow out of control really fast. There is also a macromancy feature where you can get taller while you gain weight. I have set it up before where my character became large enough to fill Whiterun keep and her head peaked above Dragonsreach. You can also overencumber yourself by eating too much.
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Fertility Mode at Skyrim Special Edition Nexus - Mods and Community - Comprehensive pregnancy mod. Just another way to realistically grow. You can add debuffs based on when you have your period, ovulate, and for each trimester. You can fully customize the size you grow and the debuffs, but the morphs get pretty weird when you max out the scale.
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Adiposian Playable Race SSE - A custom race focusing on various BBWs. It is not compatible with the morph mods, but it may still be fun to include. There is also a feeding throne in the Church of Buxomology that actually makes your belly bigger, so I keep it for immersion purposes.
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unrelenting BURP (female) at Skyrim Special Edition Nexus - Mods and Community - Makes Unrelenting Force become a massive burp. If your Dragonborn is going to be larger than life, so should your thu’um.
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Immersive First Person View at Skyrim Special Edition Nexus - Mods and Community - The first person mod that is the most stable for the above list
Since all the mods are morph-based, your face will not be changed as you change weight. You will need to do that manually in the Race Menu if that is a make or break for you. Here is a list of additional morph mods. They are much more customizable, but require more experimentation. I am not currently running them because 1) mods 1, 2, and 4 cover my body modification needs and 2) I’m too lazy to give them the TLC they deserve:
a. Weight-Determined Body Physics at Skyrim Special Edition Nexus - Mods and Community
b. WeightMod - Smooth Real-Time Weight and Muscle Transformation at Skyrim Special Edition Nexus - Mods and Community
c. BodyMod - Smooth Real-Time Morph Manipulation at Skyrim Special Edition Nexus - Mods and Community