the implant

GainStation13/code/modules/surgery/organs/augments.dm

@@ -9,3 +9,17 @@
 	hunger_threshold = NUTRITION_LEVEL_FULL
 	poison_amount = 10
 	message = "" //no message cuz spam is annoying
+
+/obj/item/organ/cyberimp/chest/mobility
+	name = "Mobility Nanite Core"
+	desc = "This implant contains nanites that reinforce leg muscles, allowing for unimpeded movement at extreme weights."
+	icon_state = "chest_implant"
+	implant_color = "#9034db"
+
+/obj/item/organ/cyberimp/chest/mobility/Insert(mob/living/carbon/M, special = 0)
+	..()
+	ADD_TRAIT(M, TRAIT_NO_FAT_SLOWDOWN, src)
+
+/obj/item/organ/cyberimp/chest/mobility/Remove(mob/living/carbon/M, special = 0)
+	REMOVE_TRAIT(M, TRAIT_NO_FAT_SLOWDOWN, src)
+	..()

GainStation13/code/obj/items/minor_items.dm

@@ -67,6 +67,11 @@
 	uses = 1
 	starting_organ = /obj/item/organ/cyberimp/chest/nutriment/turbo
 
+/obj/item/autosurgeon/fat_mobility
+	desc = "A single use autosurgeon that contains a mobility nanite core. A screwdriver can be used to remove it, but implants can't be placed back in."
+	uses = 1
+	starting_organ = /obj/item/organ/cyberimp/chest/mobility
+
 //fast food restaurant - closed / open signs
 /obj/item/holosign_creator/restaurant
 	name = "Holosign Projector - Restaurant Adverts"

code/__DEFINES/traits.dm

@@ -230,6 +230,7 @@
 #define TRAIT_NO_BUCKLE "no_buckle"
 #define TRAIT_DOCILE "docile"
 #define TRAIT_LIVESTOCK "livestock"
+#define TRAIT_NO_FAT_SLOWDOWN "no_fat_slowdown"
 
 // common trait sources
 #define TRAIT_GENERIC "generic"

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

@@ -1893,7 +1893,7 @@ GLOBAL_LIST_EMPTY(roundstart_races)
 
 		// Hyperstation 13: Mood now influences action speed.
 
-		if(H.fatness) // GS13
+		if(H.fatness && !HAS_TRAIT(H, TRAIT_NO_FAT_SLOWDOWN)) // GS13
 			var/fatness_delay = (H.fatness / FATNESS_DIVISOR)
 			if(H.fatness < FATNESS_LEVEL_BARELYMOBILE)
 				fatness_delay = fatness_delay - flight