"About 30 percent of the animals on calorie restriction die at an advanced age without any diseases normally related to aging," Fontana says. "In contrast, among animals on a standard diet, the great majority (94 percent) develop and die of one or more chronic diseases such as cancer or heart disease. In 30 percent to 50 percent of the animals on calorie restriction, or with genetic mutations in these aging-related pathways, healthspan is equal to lifespan. They eventually die, but they don't get sick."
Unfortunately, many humans are moving in the opposite direction. As obesity reaches epidemic rates in Western countries, Fontana says rather than closing the 30-year gap between healthspan and lifespan, the gap is likely to grow. It's even possible lifespan may decrease as people develop preventable diseases such as atherosclerosis, type 2 diabetes and certain forms of cancer.
Those growing rates of obesity are a reason some scientists think calorie restriction will never catch on, regardless of its potential benefits. But, Fontana says, if researchers who study nutrition and aging can understand how calorie restriction lengthens life and makes people healthier, it may be possible to develop less drastic interventions or medicines that influence pathways affected by calorie restriction and help keep people healthy as they get older.
Among people now practicing calorie restriction, he says side effects include reduced libido because calorie restriction reduces testosterone levels. They also tend to become cold more quickly because their thermal regulation changes as their metabolism slows and their core body temperature drops.
Fontana says as calorie restriction research advances on many fronts, it's becoming clear t
|Contact: Jim Dryden|
Washington University School of Medicine