I’ve found an anime/manga series that has a male weight gain and male belly stuffed is call: ‘The Law of Ueki’.
In episode 9, Ueki and his friends stumbled upon a crazy kid that feels obligated to repay every kindness“ a hundred times more”. And since Ueki gave him a bottle of water to repay his thirst, the kid forces him to drink a hundred bottles of water at the same time, leaving him with a hugely bloated belly and in a near comatose state. At one point he even spits out water, creating a little rainbow over his head.
https://youtu.be/KPMuAJV7xjo
Belly Stuffed Scene start at 15:23
In Chapter 62, For every 100 grams of cake eaten by one, his rival will put on 1 kilogram. And the trouble is, the overweight kid just keeps stuffing his face with cake (his name is Yunpao by the way). As a result, Ueki starts to grow fat - And if he doesn’t find Yunpao weakness soon, he will end up too big to move.
https://r.mangaowls.com/reader/49634...YW93bC5uZXQ%3D
Episode 18 & 19 (an anime version of Chapter 62) is the same as the manga.
Male Weight Gain Scene in Episode 18 start at 19:50
https://youtu.be/AwRcU6VCet8
And Male Weight Gain Scene continue in Episode 19.
https://youtu.be/tzLxxUZ1bDk