I am a Malaysian. A few days ago, one of my country's political speakers claimed he didn't eat anything for 10 days, and he just survived by drinking water.
This phenomenon really make me interested in how human can do that just by using the spiritual strength.
As far as I know, humans will die if they don't eat anything in 7 days. All this knowledge comes from my primary school.
TLDR : at least 94 days.
I don't think science can directly answer the question, because there are too many variables, but I can partially answer by referencing to how long someone did survive without food. The Guinnes World Record states that
... the world record in hunger strike without force-feeding as 94 days, which was set from August 11 to November 12, 1920 by John and Peter Crowley, Thomas Donovan, Michael Burke, Michael O'Reilly, Christopher Upton, John Power, Joseph Kenny and Seán Hennessy at the prison of Cork.[5][6] Arthur Griffith called off the strikes after the deaths of MacSwiney, Murphy and Fitzgerald.
They can go on for a very long time.
This is a documented medical example of a (admittedly very obese) person who stopped eating for 382 days under medical supervision.
Patient A.B. aged 27 years, weighed on admission 456 lb (207 kg). During the 382 days of his fast, vitamin supplements were given daily as 'Multivite' (BDH), vitamin C and yeast for the first 10 months and as 'Paladac' (Parke Davis), for the last 3 months. Non-caloric fluids were allowed ad libitum. From Day 93 to Day 162 only, he was given potassium supplements (two effervescent potassium tablets BPC supplying 13 mEq daily) and from Day 345 to Day 355 only he was given sodium supplements (2 5 g sodium chloride daily). No other drug treatment was given.
Features of a successful therapeutic fast of 382 days' duration W. K. Stewart and Laura W. Fleming
Fasting is very well studied and there is a complete review on Wiley.
There must be a great range of values depending on the individual's condition and on the circumstances.
20 to 40 days is possible.
According to Scientific American
At the age of 74 and already slight of build, Mahatma Gandhi, the famous nonviolent campaigner for India's independence, survived 21 days of total starvation while only allowing himself sips of water.
In a 1997 article in the British Medical Journal, Michael Peel, senior medical examiner at the Medical Foundation for the Care of Victims of Torture, cites well-documented studies reporting survivals of other hunger strikers for 28, 36, 38 and 40 days.
Off-topic digression:
Whether politicians making unusual claims should be believed perhaps depends on whether they have reliable corroboration from truly independent and impartial observers. Perhaps he sleepwalked to the kitchen fridge? Is alleged willingness and ability to endure starvation in any way correlated to sound judgement to honesty, integrity or to any other desirable trait in politicians?
According to Slate, "Sixty days, give or take, is the rule of thumb, though results vary depending on the faster's body fat and striking strategy. Physiologists generally agree that no human being can survive losing more than 40 percent of his body mass."
The article seems well researched, so I see little value quoting more of it.
