A diet that proclaims cutting calories is the secret to a longer life has been called into question by new research.
In 2005, The Longevity Diet offered to help readers slow their ageing process and maintain peak vitality by dramatically cutting calorie intake.
However, an expansive study analysing the diet's effects on rhesus monkeys, the closest relative to humans, showed no increase in their life expectancy.
Although the calorie-restricted monkeys in the study boasted healthier hearts and lower rates of diabetes and cancer than those who did not follow the diet, there was no effect on their lifespan.
"If there's a way to manipulate the human diet to let us live longer, we haven't figured it out yet and it may not exist," said Steven Austad from University of Texas Health Science Center's Barshop Institute for Longevity and Aging Studies, who analysed the study.