still easy, but not as much as I had expected.

.vscode/settings.json

@@ -5,5 +5,11 @@
 
 	"workbench.editorAssociations": {
 		"*.dmi": "imagePreview.previewEditor"
+	},
+	"files.exclude": {
+		"**/*.rpyc": true,
+		"**/*.rpa": true,
+		"**/*.rpymc": true,
+		"**/cache/": true
 	}
-}
+}

GainStation13/icons/obj/vairous_weapons.dm

@@ -0,0 +1,2 @@
+/obj/item/bdsm_whip/ridingcrop/fattening
+	damtype = FAT

code/modules/mob/living/carbon/damage_procs.dm

@@ -43,6 +43,8 @@
 		//citadel code
 		if(AROUSAL)
 			adjustArousalLoss(damage * hit_percent)
+		if(FAT)
+			applyFatnessDamage(damage * hit_percent)
 	return TRUE
 
 
@@ -121,10 +123,9 @@
 
 
 /mob/living/carbon/applyFatnessDamage(amount)
-	if(!check_weight_prefs(FATTENING_TYPE_WEAPON)) //Typically, this kind of damage would be applied to people through weapons.
-		return FALSE
-
-	adjust_fatness((amount * FAT_DAMAGE_TO_FATNESS), FATTENING_TYPE_WEAPON)
+	var/fat_to_add = ((amount * CONFIG_GET(number/damage_multiplier)) * FAT_DAMAGE_TO_FATNESS)
+	adjust_fatness(fat_to_add, FATTENING_TYPE_WEAPON)
+	return fat_to_add
 
 
 /** adjustOrganLoss

code/modules/mob/living/carbon/human/species.dm

@@ -2461,6 +2461,8 @@ GLOBAL_LIST_EMPTY(roundstart_races)
 			H.adjustOrganLoss(ORGAN_SLOT_BRAIN, damage * hit_percent * H.physiology.brain_mod)
 		if(AROUSAL)											//Citadel edit - arousal
 			H.adjustArousalLoss(damage * hit_percent)
+		if(FAT)
+			H.applyFatnessDamage(damage * hit_percent)
 	return 1
 
 /datum/species/proc/on_hit(obj/item/projectile/P, mob/living/carbon/human/H)

code/modules/mob/living/damage_procs.dm

@@ -43,6 +43,8 @@
 			return adjustCloneLoss(damage)
 		if(STAMINA)
 			return adjustStaminaLoss(damage)
+		if(FAT)
+			return applyFatnessDamage(damage)
 
 /mob/living/proc/get_damage_amount(damagetype = BRUTE)
 	switch(damagetype)
@@ -60,7 +62,7 @@
 			return getStaminaLoss()
 
 
-/mob/living/proc/apply_damages(brute = 0, burn = 0, tox = 0, oxy = 0, clone = 0, def_zone = null, blocked = FALSE, stamina = 0, brain = 0)
+/mob/living/proc/apply_damages(brute = 0, burn = 0, tox = 0, oxy = 0, clone = 0, def_zone = null, blocked = FALSE, stamina = 0, brain = 0, fatness = 0)
 	if(blocked >= 100)
 		return 0
 	if(brute)
@@ -77,6 +79,8 @@
 		apply_damage(stamina, STAMINA, def_zone, blocked)
 	if(brain)
 		apply_damage(brain, BRAIN, def_zone, blocked)
+	if(fatness)
+		apply_damage(fatness, FAT, def_zone, blocked)
 	return 1
 
 

tgstation.dme

@@ -3159,6 +3159,7 @@
 #include "GainStation13\code\obj\weapons\alter_rays.dm"
 #include "GainStation13\code\obj\weapons\fatbeam.dm"
 #include "GainStation13\code\obj\weapons\fatoray.dm"
+#include "GainStation13\icons\obj\vairous_weapons.dm"
 #include "hyperstation\code\__DEFINES\economy.dm"
 #include "hyperstation\code\__DEFINES\wendigo.dm"
 #include "hyperstation\code\controllers\subsystem\economy.dm"