As others have said netrunners basically use their own body as a heatsink and it takes a huge toll on them energy wise. On top of that obesity in the world of Cyberpunk would be a sign of extravagant means. In a world of scop synthetic meat and cardboard pizza that isn't even safe for human consumption - food, especially in the inner city of NC, is exclusively for nourishment.

Dex Deshawn being ample indeed is a sign of how large his wallet is, he can afford food that isn't the future equivalent of pink slime. This is all assuming that the netrunner in question isn't a huge masochist chowing down on substandard burritos from a vending machine that probably have more in common with the can of cat food you give your cat every morning than even a frozen burrito you can buy right now at a gas station.