Harvie sounds a cautious note for anyone thinking of giving fasting a go. "We still don't know exactly who should be fasting, how often or how many days a week," she says. Also, it may not be without risks. One study in rats, for example, found that an alternate-day fast for six months reduced the heart's ability to pump blood.
There is also the fact that fasting is difficult. Varady finds that 10 to 20 percent of people who enroll in her studies drop out, unable to stick to the regime. This may be less of a problem in the future, though. Some researchers are investigating the possibility that you can get some of the health benefits of fasting simply by reducing protein intake.
As I count down the minutes to the end of my fast, I can't help but wish them success.
This story was produced by New Scientist magazine and can be read in full at www.newscientist.com.