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.
Prahlad Jani
Two observational studies of Jani have been conducted, one in 2003 and one in 2010, both involving Dr Sudhir Shah, a neurologist at the Sterling Hospitals in Ahmedabad, India, who had studied people claiming to have exceptional abilities, including other fasters such as Hira Ratan Manek. In both cases the investigators confirmed Jani's ability to survive healthily without food and water during the testing periods, although neither study was submitted to a scientific journal. When questioned six days into the 2010 experiment, the DRDO spokesperson announced that the study's findings would be "confidential" until results were established, and a further official press release by the team stated that any inside analysis information may be disclosed only at the discretion of the principal investigator, DIPAS. Uninvolved doctors and other critics have questioned the validity of the studies and stated their belief that, although people can survive for days without food or water, it is not possible to survive for years, especially since glucose, a substrate critical to brain function, isn't provided. The veracity of Mataji's claims has also never been independently confirmed with all tests being indigenously conducted.