According to the diet's creator Doctor Michael Mosley, women are restricted to eat 500 calories or less for two days while men are allowed to consume 600.
The calories can be consumed in one meal or over the course of the day, but translate to 25 percent of a normal adult's daily intake.
Scientists across the country performed research on rats and discovered that the body and the brain respond in fascinating ways to the severe calorie restriction.
Dr. Mark Mattson, a professor of neuroscience at Johns Hopkins University, was astonished by the results.
"What they found in rats is when they are deprived of food their brain starts producing a protein called brain derived neuro-traffic factor," Dr. Mosley said. "What this does is it makes you feel happier and what it also appears to do is make you smarter."
In addition to the improved brain function, researchers have found severe calorie restriction in a controlled environment can lead to decreased cancer risk, and increased life expectancy.
The diet has become extremely popular in Britain.
ABC News contributed to this report.