How long can you go without food and water?

The question of how long you can go without food depends on a lot of factors. Will and determination definitely play a part. Political prisoners on hunger strikes and fasting religious leaders have been known to go for weeks at a time without any food. Gandhi fasted for 21 days while in his 70s. People lost in the wild have also survived for long periods of time without eating.

Medically speaking, most doctors agree that healthy humans can go up to eight weeks without food as long as they have water. People have gone longer and been fine, and people have starved to death in less time. Being strong and in good physical shape can help you survive longer, but so does having extra body fat. The body stores energy needed to live in the form of fat, carbohydrates and proteins. The carbs are the first thing to be used up without more food coming in. The fat goes next, which explains why people with more of it can survive longer. Then the proteins go. If you get to the point that your body is using up proteins, basically the body itself, then you're in bad shape.

Your metabolism also plays a role. Metabolism is what converts food into energy. If you have a slow metabolism, you'll burn your food intake slower and be able to go longer without replacing the food energy. If you go without food, your metabolism will adjust accordingly and slow down on its own -- basically doing what it can to pitch in for survival's sake.

Climate is a major factor too. The bad news is that both cold and hot weather are no good if you have no food. The good news is that extreme heat and cold will kill you in other ways before you have a chance at starvation. But in terms of living without food, heat means faster dehydration -- cold means more energy is burned to keep the body's temperature at a cozy 98.6 degrees Fahrenheit (37 degrees Celsius). If you're lucky enough to be in mild temperatures, you'll be able to live a little longer without food.

Some symptoms you may see if you go more than a couple of days without food are:

Advanced starvation will cause your organs to shut down one by one. People in the throes of severe starvation might experience the following:

In the next section, we'll look at how important water is and what happens to your body without it.

Now that we've established that food is something we can do without for a reasonable amount of time, we can move on to water. Living without water is very different from living without food. In hot conditions with no water, dehydration can set in within an hour. A baby locked in a hot car or someone who is physically overexerted in the heat without replacing fluids can actually die in a period of several hours.

Humans need water to live, plain and simple. We lose water through sweat, urine, feces and even breathing. This water needs to be replaced in order for our organs to continue to work properly. In severe heat, an adult can lose as much as 1.5 liters of water through sweat alone [source: Scientific American]. The main risk without water in high heat is that your body temperature will continue to rise and you'll suffer from heat stroke. Drinking water will cool you down and lower your core temperature.

With mild dehydration, you'll experience the following:

Moderate dehydration:

Severe dehydration:

The final stage of dehydration is shock. This is characterized by blue-gray skin that's cold to the touch. A severe drop in blood pressure produces this coolness.

Now back to the question at hand. How long can you go without water? Assuming you're in reasonable shape and in ideal conditions -- that is, not in the heat or cold and not exerting, a human can probably live for about 3 to 5 days without any water. Healthier humans can live another day or so longer.

This isn't something you should test. While people may fast or try a body cleanse without food, you should absolutely never go without water for more than a day. The Mayo Clinic recommends drinking about eight cups of water a day, although there's some debate about this number [source: Mayo Clinic]. Some physicians say less is fine, while others say the number should be closer to 10 cups or even more.

For more information on food, water and survival, please dive into the material on the following page.