Greetings!
I have been delving into the DOOM mods recently and I came up with a mod concept that involves voluptuous demons, fattening food, and more!
If I had the programming know-how, or a sprite artist, I would be dilligently working on this. Alas, all I can do is write stories and be creative. As far as I know, I do not believe a mod like this exists for the game, hence why I want to get this out there! 
I am currently away from home, and Iāll edit with more images and better formatting when I am on my desktop.
ā¢ Introduction
What is DOOM?
DOOM is the classic first person shooter for the PC (I really shouldnāt have to explain this) This game has an extensive modding library ranging from simple map packs to complete game overhauls. The objective in the game is to survive and reach the exit switch/portal at the end of each level. Utilising various guns and powerups the player can rip and tear through hordes of enemies.
What will the mod be?
DOOM BFG (Big Fatty Game) in concept will put a twist in the run and gun gameplay that the original establish.
In a nutshell, (later sections will elborate) the mod would a dynamic weight gain and size mechanic to the player character. The character sprite (doomguy) can be male or female.
The goal of each level remains the same - reach the finish. However, in DOOM BFG, there will be obstacles to prevent you from doing so. In the mod, the player can fail if their health reaches zero, or the player cannot move anymore. (Due to extreme fattening) There are enemies that are capable of damaging your health and increase your weight. Healing items will recover your HP, but at the cost of weight gain.
As the player gains mass (through items/monsters) theirs mobility is affected until compete immobility. From there they are forced a reset or to a previous save. The player can get stuck in tight corridors when reaching a threshold. More will be elaborated in the subsections below.
How will you make this mod happen?
As I mentioned before, I do not have any experience in modding DOOM, nor any of the skills involved to do so. The best I can do is put the concept out there and hope someone more talented can make it happen 
I had fun enough making up everything and imagining it working. If there is a collective group then I will help as best as I can.
Will there be other fetish elements?
This mod would focus on fat and weight gain. However, if one were to develop this into a full fledged mod, he or she could add whatever as long as it pertains to the theme.
ā¢ Mod Mechanics
The Fattening System
In BFG, there are two approaches to the FS that comes to my mind.
**Armor Overhaul Version
Replacing the armor mechanic (or changing) will be the fatness count/number. By default the player starts up with zero armor, and can pick up a set or fragments throughout the level. With the mod change, instead of armor fragments/sets, it will be replaced with a variety of food. Collecting food will increase the fatness number, and health too (depending on the item). The armor mechanic can remain the same as the higher the value the more protection from damage the PC will have. Damage from enemies can also raise the number if possible.
The āarmorā stat caps out at 200, and will be the āimmobileā level, with every 25 percent downwards is a stage of fatness.
Stage examples:
0= Normal 25= pudgy 50= Overweight 75= Fat 100= Corpulent 125= Obese 150= Morbidly Obese 175= Near Immobility 200= Immobility.
With each stage, debuffs are added to the character. Examples of such are as follows: Lower run speed, running disabled, wider hitbox, and more. Also, with each item pickup, the characters thoughts the the text in the top of the screen can change.
The goal of the player is not to get hit, or pick up too many health/food items. This provides a challenge to play carefully as each enemy has their own damage values and status effects.
*** Standalone Fatness
This option will be better to keep armor the way it is. This version will behave just like above, with the execption of having armor.
The Player Character - Doomguy/Doomgirl
In DOOM the character you play as is a male commonly called āDoomguyā. In BFG, the mod would have a male and female version of this character. The PC (Player Character) has multiple sprites involved.
First and foremost is the POV sprite aka the gun/weapon. For the sake of convenience (and design) there are no ways determine size changes through the wielding of the gun. However the guns in the game could be themed or not, and for that will require sound and sprite work. But for the sake time and theme, the guns can be left to theirs vanilla counterparts. The only difference can be the āfistsā as if the player gets larger the animation can change with it.
The PC has a third person sprite, which can be displayed in various ways. In the original game, third person can be toggled (through a setting) and in multiplayer where youāre able to see it. This is where the āphysicalā weight gain will be shown. Clothes/armor etc. can change throughout the stages. (Distended, ripped, naked, etc.) In the POV camera, the sprite can be viewed at all times, letting the player know of their current fatness level.
Finally, there is the face sprite. It is placed in the HUD, and it gives a visual cue to the health of the PC. In the mod it can be replaced by the 3rd person sprite, or remain and expand with fatness.
Monsters/Demons/Enemies
There are many enemies in DOOM and depending on the amount of effort and modding, BFG could be a fantastic mod. However, the mod could work with minimal adjustments, as the core mechanic of weight gain can still occur through item pickups. Below will be a picture of a modded DOOM game featuring modfied sprites and gameplay. The sky is the limit when it comes to it! But for the mod theme could center around food, thick and fat women, or monsters shaped like food.
(At a later time, I will edit the post with monster ideas)
Levels and Graphics
Once again, this is something that can be left the same. However there are item replacements that would be affected by the hypothetical mod. (Food instead of medkits/armor)
As for graphics, there can be changes to the HUD, menu and more if desired.
ā¢Example of A Modded Doom Game
This image is an example of a modded version of DOOM. This screenshot has the mods āLa Tailor Girlā and āStylish Hellā. The mod concept could look similar to that if done correctly. (Obviously with a fatty/weightgain theme) This is an example of a third person sprite in the HUD, unique enemies, and more shows what modded DOOM is capable of. I believe this idea is possible, however will take tremenous amounts of work, especially to get to this level.
ā¢Conclusion
Once again, I do not know how to mod DOOM to achieve what Iāve discussed. I wanted to share to the community this mod concept since it seems to be in the realm of possibility. I could learn how to myself (and Iām sure I can) but with a busy life, its going to be incredibly hard. If nothing comes out of this post, I had fun sharing it in the first place!
