Calorie Restriction Not Shown to Extend Life

Kathleen Blanchard's picture
Calorie Restriction
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Proponents of calorie restriction tout the practice as a means toward a long life. According to a new study, calorie restriction is not healthy, nor does it increase our lifespan. Much research has been devoted to the notion that calorie restriction decreases our chances of developing heart disease, cancer, Alzheimer's disease, even delaying the effects of aging. Some research articles have referenced calorie restriction as "the fountain of youth". Current research shows that calorie restriction does not extend life.

According to new study from the University of California, funded by the National Institutes of Health, calorie restriction is under question as a means to extend life, unless you are a fat mouse. According to the authors, calorie restriction "may be a pointless, frustrating and even dangerous exercise." The caloric restriction study is published in the January issue of the Journal of Nutrition.

According to study author, Raj Sohal, professor at the University of Southern California's School of Pharmacy, "there are a lot of very healthy people who look like skeletons because they bought into this". In order to prove whether calorie restriction can extend life, the researchers studied two strains of genetically engineered mice

When the researchers compared the two strains of mice, they found that the mice possessing the "fat" strain gene, known as C57BL/6 gained weight over a lifetime. The mice that contained the lean" strain gene, DBA/2, did not become fat. Only the "fat strain" of mice benefited from calorie restriction. As shown by the researchers' prior work, the "lean strain" of mice did not benefit from calorie restriction.

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Sohal says, "Our study questions the paradigm that caloric restriction is universally beneficial. Contrary to what is widely believed, caloric restriction does not extend (the) life span of all strains of mice."

The researchers were led to a conclusion: "Your energy expenditure and your energy intake should be in balance. It's as simple as that. And how do you know that? By gain or loss of weight. The whole thing is very commonsensical." Sohal also found in a 2003 study, that calorie restriction shortened lifespan in the tests. Mice in the wild tested with calorie restriction also did not extend their lives to any significant degree.

Obese individuals can still benefit from cutting calories, combined with exercise. The authors strongly recommend against calorie restriction as a means for better health and a long life, if your weight is already normal.

The new study shows that calorie restriction only benefits mice that are obese, not humans, and that it may possibly do more harm than good.

Abstract: Life Span Extension in Mice by Food Restriction Depends on an Energy Imbalance

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Comments

a) The researchers failed to use the protocol in animals put on CR late in life... slowly easing them onto CR. Shock CR doesn't work. CR does work late in life in the C57BL/6 mice. b) The researchers used a screwed up mouse model that tends to develop early diseases and is not long lived. c) They used a mice that is totally different from the human population in that it never gains any weight. This is not the case for humans. A more perfect example of a similar model to humans is the B6 mice, which late-onset CR DOES work if the animals are slowly put on CR, and their protein intake is increase and nutrient levels sufficient. The researchers did follow these rules. d) The Wild Type mouse study actually did show a big increase in lifespan, only this was reduced because of early deaths in the CR group and this is probably a study design fault rather than CR not working. The fact is that CR in humans is being shown to work, and we ARE responding in the same way from early studies done on humans. I recommend reading this http://www.imminst.org/forum/index.php?showtopic=27264 and Comment 1 here http://ouroboros.wordpress.com/2006/10/30/does-caloric-restriction-extend-life-in-wild-mice/
Sorry, on point C) I should correct that the researchers NEVER followed the rules of how to put old aged mice on CR. Interestingly just reported on CBS (60 minutes show) the Rhesus monkey study is showing a benefit from CR... the CR rhesus monkeys are out living the ad lib group. CR monkeys 25% have died, and normal fed monkeys; 50% have died. CR monkeys look younger with better skin and hair, move and act younger, and are physiologically younger at same age as control fed group. CR works in almost all species tested on, including recently done studies using Dogs and Monkeys. Overwhelming evidence it's also working in humans.
Starting in the mid 30's scores of carefully controlled studies have shown that calorie restriction extends the life span of virtually all species tested - yeast, rodents, primates, dogs, and cats - a rare exception fruit flies. For a species with the long life span of a human it may take many years to accumulate acceptable data - the same for elephants and turtles. Professors of Pharmacy only rarely have the background to do sophisticated clinical studies.