A study out of the University at Buffalo has linked severely restricting calories to slowing the progression of physical disability in age, which could have lifespan implications if carried over to humans.
The study, published in the October issue of Journals of Gerontology Series A: Biological Sciences and Medical Sciences, used a rat model of life-time caloric restriction. The researchers attributed this increased lifespan to a reduction in the visceral fat that can be responsible for inflammation leading to chronic disease.
Not surprisingly, longevity and enhanced quality of life is the ultimate aim of most research into diet and nutrition, but very few studies actually achieve such a link. The trick now will be to see if it can be carried over to humans - something the researchers say is highly unlikely due to the extremely restrictive nature of such a diet.
"This is the first study to report that caloric restriction reduced production in visceral fat of the inflammatory cytokine IL-6 and enhanced performance on overall physical function assessments," said Tongjian You, assistant professor of exercise and nutrition sciences at UB School of Public Health and Health Professions and principal investigator in the study.
Supported with grants from the National Institutes of Health (NIH), the study was conducted with male rats in three age groups. These ranged from 18, to 24 and 29 months, which are comparable to 50 to 70 years in humans.
The rats were fed either a normal or 40-percent calorie-restricted diet from birth, and then put through tests to determine grip strength, muscle tone, stamina and swimming speed. In addition, data were collected on varying kinds of body mass and fat-to-lean ratios, as well as the amount of pro-inflammatory cytokines and the chronic inflammation marker, C-reactive protein.
According to the study, the results indicated the animals on the restricted calorie diet had significantly higher physical performance scores than animals fed a normal diet.
However, the researchers say these positive results are not likely to be carried over to humans, as it would be nearly impossible for people to keep such diets. A 40 percent reduction in calories daily - when translated to humans - means that an average diet of 2,000 calories per day for adult women and 2,500 for men would be cut to 1,200 or 1,500 calories per day.
"It's very difficult for people to maintain that type of diet for short periods of time, and it would be nearly impossible over a lifetime, while staying healthy," said You. "Starting on a diet like that in the senior years would be harmful."
Still, a moderate caloric restriction would likely bring about positive effects on oxidative stress and inflammatory biomarkers - something which would could be worthy of further investigation in human trials.
"Preclinical testing of this 8-percent regimen could be informative and beneficial in translating to humans," said You.
Located in Buffalo, New York, the University at Buffalo is the largest campus of the State University of New York.