This theory is mostly stolen so I apologise I half discussed this in the upcoming chapter review ft. @FrankyGaon15 , but since it's been a while since I looked at this so I've re-directed people here Introductions aside, let's begin During the course of the series, we've seen Luffy eat until he becomes stupidly fat, only for him to return to his normal shape within the next set of panels. We saw it again this week, in Chapter 843: Spoiler: Super steamy pics Now, I know what you're thinking: "But Marco it's clearly a gag" "Marco why'd you get me all excited for a proper theory when you're just gonna focus on a joke, -1" "Marco sign my chest" I can resolve two of the following problems within this thread.* Spoiler: * If you would like Marco Polo to sign your chest, please send a request to: Marco Polo Marco Polo Industries Fan Division 95 Percent Street England North Blue PO Box 42 069Within this request, please send: Your forum name A meeting location for the chest signing A skin marker McDonalds coupons A 500 word brief explaining what Marco Polo means to you and why you want your chest signed Back to the theory and explaining why this is now (somewhat) noteworthy. I mentioned above that we've seen Luffy go from super fat to normal before, but this is the first time that anyone's actually commented about him doing this in a more serious way (I think Ivankov mentioned it in Impel Down after Luffy recovers from the hormone treatment but it was more comedic than anything there). With this chapter, we can say that it's not just a gag any more, that Luffy is actually able to digest massive amounts of food in an instant. So, Luffy digests food super quick. But how? The following video by the King of Lightning is where I've taken the idea from, I'm just adding 843 stuff because it strengthens the case. For those who don't want to watch the video, here's a summary: This ability of Luffy's to suddenly change his body from fat to normal is based on the Chinese martial art of Qi Gong There have been instances of this before in the series; Kumadori of the CP9 can do this through an ability known as "Life Return" A potential further application of this is Lao G being able to release energy he's stored over the years (when he suddenly became buff against Chinjao and Sai) Luffy isn't aware of this ability yet; he simply does it innately but there is potential for him to control it in the future As far as a potential cause for this ability goes, there's not enough in the story right now to say for sure, but if I were to hazard a guess, I'd say it's most likely a genetic thing than anything else. Before I explain the genetic thing, one thought that's come in to my head during the write-up of this theory is "Could it just be his Devil Fruit?" The answer to that is no, for the following reason: Whilst the Gomu Gomu no Mi allows him to stretch more than a normal person, accounting for the drastic change in appearance. However, it doesn't explain how he's able to digest so quickly, as his Devil Fruit likely doesn't affect his metabolism. Sure, you could say his digestive enzymes are stretchy so he can digest faster, but that mechanism would probably cause him a load of other health issues, as well as being over complicated, which is why I'm less keen on this idea. Back to genetics now. Nami asking whether Luffy "is even human" seems like one of the more obvious hints that it's not just a result of a Devil Fruit, rather a result of his actual genetic makeup as a whole. Whether it's an inherited trait from the Monkey D. family, or some kind of rare mutation is up for discussion, but with the recent revelations about genetics, both with the Vinsmokes and with the explanation of how Devil Fruits work that Law gave in Chapter 698 (you can find this either in @Jawahib and I's Devil Fruit video, or look at the chapter itself), the idea of genetics playing a role is no longer as far-fetched in One Piece as it might initially have seemed. That's me done now Thoughts?