There's a lot of good reasons why zombies are a pretty unhealthy bunch, being undead is just one of them. They don't move much, they never run and probably don't even check the labels on food packages.
Traditional weight loss for zombies often involves losing a limb, more often than not through someone not wishing to be bitten who has a weapon of sorts for defense. When it comes to healthy life choices, there's not a lot of scope for a zombie.
You've probably encountered zombies on your xbox 360 or PS3 already, and seen how lethargic they are. You probably also know that the number one zombie survival technique is avoidance. My advice to you is make sure you're as fit and healthy as you can be, in case of an actual zombie attack. Improve your fitness levels now, while you still can - right here.