Human
In general, humans can survive for two to eight weeks without food, depending on stored body fat. Survival without water is usually limited to three or four days. About 36 million humans die every year from causes directly or indirectly related to starvation. Childhood malnutrition is also common and contributes to the global burden of disease. However global food distribution is not even, and obesity among some human populations has increased rapidly, leading to health complications and increased mortality in some developed, and a few developing countries. Worldwide over one billion people are obese, while in the United States 35% of people are obese, leading to this being described as an "obesity epidemic." Obesity is caused by consuming more calories than are expended, so excessive weight gain is usually caused by an energy-dense diet.
Bloodthirsty: One Nation Under Water
When Trey dies in a fire at Wolfinger Biomed, Virgil has reason to suspect that his brother was murdered. Having nothing left to live for, Virgil decides to investigate his brother's death, even if that means staying in New Orleans long enough to die in the coming hurricane. What he uncovers is an underground cabal of hemovores - "an organism that ingests blood as the main part of its diet." Unlike vampires, the hemovores in "Bloodthirsty" are not supernatural beings; they are humans with a mutated gene that controls longevity. Their bodies are in a constant state of repair, which deprives their cells of oxygen. In order to compensate for this loss, they must consume fresh (oxygenated) human blood daily or they will die.