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.
Black Fast
The term "Black Fast" has a different connotation with writers within Classical Pentecostalism. A Black Fast is complete abstinence from food or water and nothing is consumed in its duration. Dr. Curtis Ward teaches that the Black Fast should never extend beyond three days because of ketosis, possible kidney damage, and dehydration. He further states that nothing in the New Testament says that they extended this type of fast beyond that limitation and that Christ's fast included water because "he was afterward an hungred" and was offered bread. If he had abstained from water he would have obviously craved water first and foremost. Dr. Ward states that the Black Fast, Hebrew Fast, and the Absolute Fast are synonymous terms.