"Another issue to think about is total body mass. After society collapses, the resulting food shortage will hit the larger survivors the hardest. More body mass = more calorie expenditure = need more food.

If you are carrying over 200 lbs, or have 20+% body fat, then Z-day will hit your fairly hard. Sure, you’ll lose weight fast in a starvation state, and you could logically use this as your Plan B, but this type of dramatic weight loss is devastating on the body.

Lower body weight (and lower body fat%) will do the following:

Increase your strength-to-weight ratio: Zombies can’t climb, but neither can a lot of big guys. If doing a pull-up onto a fire escape lets you evade the legions of undead, being at a healthy body weight will help greatly.

Increase your endurance: If you are a 240lb man with 30% body fat, and try to run 2 miles, it’s the same thing as.

240lb man @ 30% bf
216lb man @ 20% bf, running with 25lbs.
192lb man @ 10% bf, running with 50lbs.

The level of extra work needed to move useless body fat is huge. The 192lb 10%er has a massive advantage over the 30%er, as if he “dropped that 50lb plate” his total speed and endurance is incomparably greater.

Decrease your chance of terror-induced heart attack: Extra weight carries a great load of stress on the cardio-vascular system. Throw in some running and fighting, and blood pressure will sky rocket. Throw in a good old fashioned walk-around-the-corner-face-to-face-with-a-zombie, and you have the perfect combination for a massive heart attack.

Decrease caloric demands: Less weight = less energy = less food. Plain and simple. Like the 192lb 10%er and his 50lb plate (wad of fat). If he drops the plate (fat), his energy expenditure drops with it. Body Weight in a Post Apocalyptic World, a group will not do well if it has multiple high-calorie-demand individuals. "