How Long Can You Live Without Food?

You can survive only days without water, but you may be able to live for weeks if only food is deprived. This is because your body is extremely resourceful: It can obtain energy and fuel from its own fat and, eventually, muscle stores.

Still, the timeframe for survival without food is not concrete. Aside from the fact that there is no robust scientific data available to answer this question (researchers could never purposefully starve study participants to examine this due to ethical concerns), every individual is different, and personal factors like starting weight play a role.

How the Body Fights Starvation

The resiliency of the human body to live without nourishment is impressive, considering that your glucose (sugar) reserves—what your body normally uses as its main source of energy—are exhausted within one day of not eating.

After a day without food, your body releases a hormone called glucagon, which stimulates the liver to make glucose (a process called gluconeogenesis). This glucose is used mostly to feed the brain.

Your muscles, on the other hand, rely on fatty acids produced from the breakdown of adipose (fatty) tissue for fuel. Around day two or three of starvation, this becomes your body's main source of fuel.

Eventually, fatty acids are used to form ketone bodies in the liver. These are released into the bloodstream and used by the brain for fuel, cutting down dramatically on the brain's glucose requirement.

The shift to ketone production by the liver is what allows humans to survive a duration without food.

Once the fatty acid reserves are depleted, the only source of fuel available is protein (from your muscles). As protein breakdown accelerates, there is a loss of heart, kidney, and liver function, which ultimately leads to a person's demise.

What Influences Survival

Secondly, based on the limited studies that have been done (on people who chose to self-starve and then later presented themselves to their doctor , or people who were starved against their will ), there appear to be a few factors that influence survival time from starvation.

One critical factor is a person's starting weight. It appears that lean individuals can generally function and tolerate a weight loss of up to 18% of their body mass, whereas obese individuals can tolerate more, perhaps over 20%.

In terms of a precise timeframe, research has found that in people who are not obese or overweight, starvation causes frailty (weakness) between 30 and 50 days and death between 43 and 70 days. In obese people, these timeframes are likely longer.

Other factors that may play a role in determining survival time from starvation include:

Gender: Women survive longer than men, even in crises like famines.
Age: Children are at a higher risk of dying during famines.

Complications of a Lack of Food

Death is the eventual universal outcome of a lack of food. Leading up to death, there are numerous complications that occur as a result of starvation, and the number of systems affected within the body increases with the degree of weight loss.

Some of these complications include:

Bone loss (called osteoporosis)
Muscle weakness and wasting
Feeling cold
Thinning or loss of hair
Dry skin
Constipation
Loss of menstrual cycle (amenorrhea)
Fatigue, shortness of breath, and paleness from anemia

A Word From Verywell

Many people who ask this question do so out of curiosity that is perhaps sparked by "what ifs" and rescue stories, and the above may never be something they're personally impacted by. But if you are restricting food intake—perhaps due to an eating disorder like anorexia nervosa or due to a very strict dietary plan—these concerns can have a very real impact.

Please seek out care from a healthcare professional. Your body needs (and you deserve) nourishment to function and thrive.