Nearing the half-way point in his starvation stunt, David Blaine says he has a sweet taste in his mouth "like pear drops". So what is going on inside his body?
Twenty days after the start of his starvation stunt, showman David Blaine says he has entered "starvation mode".
WHAT'S HAPPENING TO BLAINE?
1. Brain has primacy - all systems geared to its survival
2. Sweet taste due to ketones
3. Heart wall starting to erode
4. Appetite will have gone
5. Very low blood pressure
6. Muscles weakened by inactivity
Increasingly weak and unsteady, Blaine, who aims to go without food for 44 days, says he has started to notice a sweet taste in his mouth, like that of pear drops. He was speaking via a webcam in his plexiglass box near London's Tower Bridge.
Although his incarceration means it's impossible to know exactly what state his body is in, if his endurance test is real rather than an elaborate illusion, he is in an advanced first stage of starvation.
Within a few days of not eating, Blaine's body will have automatically prioritised what it needs most and what it can do without.
Taking precedence at all times is the brain, and everything else is sacrificed to try to ensure its survival.
"The brain is the primary organ in your body and your body's whole balancing system is there to look after the brain," says Dr Adam Carey, who carried out Blaine's medical before he embarked on his stunt.
Normally, the brain is fed by sugars that we eat as part of a daily diet.
But since Blaine is subsisting solely on water, his body will have started to seek out its own sugars, and it will have found these in its fat reserves.
Breaking down these reserves releases glycerol which is converted into glucose for the brain, and fatty acids. The latter are burned to produce ketones, which can also be used as brain fuel.
The ketones gradually become the dominant source of fuel and it is these which are producing the pear drops taste in Blaine's mouth, says Dr Carey.
Blaine will have lost a fair bit of weight from this fat burning. Doctors speculate that he has already dropped 10lbs (4.5 kilos).
But soon the fatty reserves will have been drained and about now it's likely that Blaine's body will resort to a secondary source of brain fuel, in the proteins of the muscles and organs.
Initially, it will harvest these from the liver and spleen, later it will move on to the wall of his heart.
Blaine also will be suffering very low blood pressure due to total absence of salt in his diet.
"If he were to stand up suddenly, he would probably faint," says Dr Carey, "although he won't have the energy for fast movement now anyway."
Sodium is also an electrolyte and helps conduct messages to and from the brain - with this depleted his reactions will have slowed.
Last week's unseasonably warm weather will have seen him sweat more than normal and this could have a knock-on effect as Blaine enters the second half of his endurance test, says Dr Carey.