[ExI] CR--maybe not so much use

[Damien Broderick]

Mouse Study Questions Fat-Loss And Longevity Link
04 May 2011

Since the 1930s scientists have proposed food restriction as a way to 
extend life in mice. Though feeding a reduced-calorie diet has indeed 
lengthened the life spans of mice, rats and many other species, new 
studies with dozens of different mouse strains indicate that food 
restriction does not work in all cases.

Diet and fat loss

Researchers at the UT Health Science Center San Antonio's Barshop 
Institute for Longevity and Aging Studies, with colleagues at the 
University of Colorado, studied the effect of food restriction on fat 
and weight loss in 41 genetically different strains of mice. The 
scientists then correlated the amount of fat reduction to life span.

The answer: Mice that maintained their fat actually lived longer. Those 
that lost fat died earlier.

Contrary to view

"Indeed, the greater the fat loss, the greater the likelihood the mice 
would have a negative response to dietary restriction, i.e., shortened 
life," said James Nelson, Ph.D., professor of physiology at the Barshop 
Institute. "This is contrary to the widely held view that loss of fat is 
important for the life-extending effect of dietary restriction. It turns 
the tables a bit."

The results are expected to be published in the June issue of Aging Cell.

More study needed

Dr. Nelson's graduate student, Chen-Yu Liao, who will soon receive his 
Ph.D. and advance to a postdoctoral fellowship at California's Buck 
Institute for Research on Aging, cautioned that the new findings cannot 
be directly applied to people until similar studies are done in humans.

People are best advised to adopt a moderate approach, not losing all fat 
but definitely not keeping unhealthy amounts of fat, either.

"None of the mice in this study were what we would consider to be 
obese," Liao said.

Genes impact effect

The findings bear out what geneticists long have said: there is nothing 
that works for every genotype, which is an organism's specific and 
unique set of genes.

"We know that humans respond to diet very differently as individuals 
based on their genetics," Dr. Nelson said. "Some have great difficulty 
losing weight while others have difficulty maintaining weight. If these 
results translate to humans, they would suggest that individuals who 
have difficulty losing weight may benefit from the positive effects of 
dietary restriction more than those who lose weight easily."

Notes:

Authors:
Fat Maintenance Is a Predictor of the Murine Lifespan Response to 
Dietary Restriction. Chen-Yu Liao1,2, Brad A. Rikke3, Thomas E. 
Johnson3,4, Jonathan A.L. Gelfond2,5, Vivian Diaz2, James F. Nelson1,2 
DOI: 10.1111/j.1474-9726.2011.00702.x

1Department of Physiology, UT Health Science Center San Antonio;
2Barshop Institute for Longevity and Aging Studies, UT Health Science 
Center San Antonio;
3Institute for Behavioral Genetics, University of Colorado, Boulder;
4Department of Integrative Physiology, University of Colorado, Boulder;
5Department of Epidemiology and Biostatistics, UT Health Science Center 
San Antonio

Source:
Will Sansom
University of Texas Health Science Center at San Antonio

Article URL: http://www.medicalnewstoday.com/articles/224149.php