Indian leader Mohandas K. Gandhi, sitting on a mattress on the floor, surrounded by people at the end of his last fast. Margaret Bourke-White/Stringer/ Getty Images

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:

Weakness

Confusion

Chronic diarrhea

Irritability

Bad decision making

Decreased sex drive

Immune deficiency

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

Hallucinations

Convulsions

Muscle spasms

Irregular heartbeat

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