14 DAY TRIAL // This may be a question not many people have asked themselves, and it may sound crazy, too. But in theory, if a human being were covered in a layer of fat thick enough, a bullet could be stopped from reaching vital parts of the body.
The Cavendish Laboratory at the University of Cambridge really performed such a test for The Naked Scientist website, where they attempted to calculate exactly how fat should a man, or woman, be in order to be able to be shot and live to tell the tale.
The degree of resistance of a material depends on the chemical compounds it's made of, how they are layered, the caliber and composition of the bullet, the powder load of the cartridge (which affects its speed), and other factors, such as weather.
Mostly, the main effective way of stopping projectiles from penetrating a person's body is to diffuse the bullet's impulse energy, so that the final impact causes little or no damage at all. That means you have to find a way to absorb the bullet's energy once it's been shot from a gun.
The fatty (or adipose) tissue is the human body's means of storing metabolic energy over extended periods of time. In fact, fats in the body are nature's way of insulating body organs against shock, among other functions. But scientists really wanted to know how thick the layer of fat must be to completely dissipate the impact energy of a bullet.
For this, they used a perspex tube which was filled with gelatin, having a density similar to fat, much like the ballistic gel used to create molds of human bodies for various testing. A bullet was fired at the 36 centimeters (1.1 ft) thick gelatin tube, from a gas gun, a chamber filled with high pressure helium, that expands extremely rapidly forcing the bullet out of the barrel at supersonic speeds.
The speed of the bullet was recorded at around 500 m/s (1600 ft/s). The exit speed was calculated at 180 m/s (550 ft/s). The result is disappointing for all Superman wannabes. A person would have to have a layer of fat at least 72 centimeters (2.2 ft) thick to be able to take a bullet and live.
So it's better to just use a bulletproof vest if you want to get into a shooting and get out of it alive.