Fat Vampire by Johnny B. Truant

Now a new TV series on SYFY: Reginald The Vampire!
Death Has a Brand New Appetite…

When overweight treadmill salesman Reginald Baskin finally meets a co-worker who doesn’t make fun of him, it’s his own bad luck that tech guy Maurice turns out to be a two thousand-year-old vampire.

And when Maurice turns Reginald to save his life, it’s just Reginald’s further bad luck that he wakes to discover he’s become the slowest, weakest, most out-of-shape vampire ever created … doomed to “heal” to his corpulent self for all of eternity.

But as Reginald struggles with the downsides of being a fat vampire (too slow to catch people to feed on, mocked by those he tries to glamour, assaulted by his intended prey and left for undead), he discovers rare powers in himself that few vampires have … and just in time, because the Vampire Council wants him destroyed as an inferior representative of their race.