Hey there! are there games that involve males gaining or even M/M based?
Gaining perspective was originally a male only game but they added in the option to choose the gender of the person who gains
Chub club is a text adventure game that also features male weight gain (you chose the gender), but is short. There is also Untitled Furry Fighting Game, though you have to create the male human yourself unless you prefer furries, where you can get into situations that also feature other fetishes. If I am correct there is also the Visual Novel the Growing Prince, but not sure how far the weight gain is in that one.
Edit: If you have Starbound you can download a mod that allows weight gain in the game, and you can play as a male protag if you want.
Worshippers of the Gain, here on the forum, lets you choose the gender of your starting character and has M/M sex & romance options.
Super Fatty RPG, although unfinished, has a gender-neutral protagonist (so you can decide your own gender) and a good amount of content.
Yaiffaif and Untitled Farming Game are both early in development and have fairly little content, but both allow you to choose the gender of and fatten up the main character in their current form.
And there are some older projects, buried deep in the archives, that have male fattening content - Super Fatty Text Adventure Game and Tainted Elysium come to mind.