Duration Life without food is strongly influenced by a number of factors such as weight, genetic variation, other health considerations and most importantly, the presence or absence of dehydration. Other hunger stunts documented in world history record survival rates ranging from 46 hours to 70 days.
Although many factors are present in determining how long humans can live without eating, our bodies go through certain metabolic processes that help us to save energy when food is not available within reach. Basically, the body stretches out time to look for nutrients.
After 3 weeks of not eating, the body continues to look for sources of protein to be converted into fuel. After the muscle is gone, the only remaining energy source is tissue and and body organs to store the second largest protein in the body. By breaking down tissue proteins and organs, you may last up to three weeks or even 70 days, depending on whether you remain hydrated or still have plenty of fat reserves to use as energy. However, at some point, your immune system will start to die due to lack of vitamins and minerals. Without a supply of vitamins or minerals, along with "death" the immune system, body functions 'unnecessary', such as menstruation and libido will also stop completely.
Usually, two diseases can occur in the final stages of hunger: marasmus and kwashiorkor. Marasmus is a severe form of malnutrition and energy deficiency, characterized by loss of muscle mass and edema, or flatulence. Kwashiorkor is the most common form of malnutrition in developing countries, caused by insufficient protein intake and also characterized by fatigue, edema, and decreased muscle mass.
If by some miracle you don't fall ill from extreme hunger, your body will slowly fall into a vegetative state - its biological function as a human still works well, but your brain is generally not functioning anymore which is then followed by death.