Prahlad Jani, an 82-year-old Indian yogi, is making headlines by claims that for the past 70 years he has had nothing -- not one calorie -- to eat and not one drop of liquid to drink. To test his claims, Indian military doctors put him under round-the-clock observation during a two-week hospital stay that ended last week, news reports say. During that time he didnt ingest any food or water and remained perfectly healthy, the researchers said.

But thats simply impossible, said Dr. Michael Van Rooyen an emergency physician at Harvards Brigham and Womens Hospital, an associate professor at the medical school, and the director of the Harvard Humanitarian Initiative which focuses on aid to displaced populations who lack food and water.

Van Rooyen says that depending on climate conditions like temperature and humidity, a human could survive five or six days without water, maybe a day or two longer in extraordinary circumstances. We can go much longer without food even up to three months if that person is taking liquids fortified with vitamins and electrolytes.

Bobby Sands, an Irish Republican convicted of firearms possession and imprisoned by the British, died in 1981 on the 66th day of his hunger strike. Gandhi was also known to go long stretches without food, including a 21-day hunger strike in 1932.

Sterling Hospitals / AFP - Getty Images file

Prahlad Jani was studied for two weeks.

Jani, dubbed "the starving yogi" by some, did have limited contact with water while gargling and periodically bathing, reported the news wire service AFP. While researchers said they measured what he spit out, Van Rooyen said he's clearly getting fluid somehow.

"You can hold a lot of water in those yogi beards. A sneaky yogi for certain," he said. "He MUST take in water. The human body cannot survive without it." The effects of food and water deprivation are profound, Van Rooyen explained. Ultimately, instead of metabolizing sugar and glycogen [the bodys energy sources] you start to metabolize fat and then cause muscle breakdown. Without food, your body chemistry changes. Profoundly malnourished people autodigest, they consume their own bodys resources. You get liver failure, tachycardia, heart strain. You fall apart.

The yogi, though, would already be dead from lack of hydration. If he really went without any liquids at all, his cardiovascular system would have collapsed. You lose about a liter or two of water per day just by breathing, Van Rooyen said. You dont have to sweat, which the yogi claims he never does. That water loss results in thicker *lo** and a drop in *lo** pressure.

You go from being a grape to a raisin, Van Rooyen said and if you didnt have a heart attack first, youd die of kidney failure.