Here's an article on  fasting that has been published online
(journal subscribers and those with library web proxy have
full text online access), and will soon appear in the print version
of the "Proceedings of the National Academy of Sciences (U.S.)".
The article is based on animal experiment data, so if that offends
you, skip the rest of this post.

Citation:
"Intermittent fasting dissociates beneficial effects of dietary
restriction on glucose metabolism and neuronal resistance to
injury from calorie intake"

R. Michael Anson, Zhihong Guo, Rafael de Cabo, Titilola Iyun,
Michelle Rios, Adrienne Hagepanos, Donald K. Ingram, Mark A. Lane,
and Mark P. Mattson

Published online before print April 30, 2003
Proc. Natl. Acad. Sci. USA, 10.1073/pnas.1035720100

Abstract

Dietary restriction has been shown to have several health benefits
including increased insulin sensitivity, stress resistance,
reduced morbidity, and increased life span. The mechanism remains
unknown, but the need for a long-term reduction in caloric intake
to achieve these benefits has been assumed. We report that when
C57BL/6 mice are maintained on an intermittent fasting
(alternate-day fasting) dietary-restriction regimen their overall
food intake is not decreased and their body weight is maintained.
Nevertheless, intermittent fasting resulted in beneficial effects
that met or exceeded those of caloric restriction including
reduced serum glucose and insulin levels and increased resistance
of neurons in the brain to excitotoxic stress. Intermittent
fasting therefore has beneficial effects on glucose regulation
and neuronal resistance to injury in these mice that are independent
of caloric intake.

Tom Billings