I made a mod this evening to introduce weight gain elements to vampire sims.
Drinking blood from a sim now adds to the fatness of the vampire sim, allowing you to have your gluttonous vampire go on a fattening blood-sucking rampage.
I also increased the calorie value of plasma and other plasma-based drinks to 1,000 per drink.
You should be able to just toss this mod file into your C:\Users[USER]\Documents\Electronic Arts\The Sims 4\Mods folder after extracting it from the .7z archive.
VampireCalorieMod.7z (35.0 KB)
Cheers.