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Still, the researchers don't pull any punches. "Our findings suggest that
obesity and cigarette smoking accelerate human aging," write professor Tim
Spector, MD, and colleagues. Spector directs the Twin Research and Genetic
Epidemiology Unit at St. Thomas' Hospital in London. The study appears in The
Lancet 's online edition.
Obesity and smoking have both repeatedly been shown to be serious health
hazards. However, they can also be overcome. If Spector's study is right, the
finding may be one more reason to go for a smoke-free life at a healthy weight,
even if it takes hard work and time to get there.
Cellular Aging Study
The women in Spector's study were all twins aged 18-76 years. The group
consisted of 45 pairs of identical twins and 516 pairs of nonidentical twins.
The researchers examined the length of the telomeres in their white blood cells.
Telomeres are the tips of the chromosomes, which contain DNA. They gradually
shorten over a lifetime. That's a normal part of the aging process. Telomere
length was checked by isolating white blood cells from the women's blood
samples.
Estimated Effects
Smoking and obesity were linked to shorter telomere length, say the researchers.
Assuming their results pan out, the researchers were able to estimate the number
of years lost to cigarettes -- or extra pounds.
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The difference in telomere length between being lean and being obese
corresponds to 8.8 years of aging.
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Smoking (previous or current) corresponds on average to 4.6 years of aging.
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Smoking a pack per day for 40 years corresponds to 7.4 years of aging.
Keep in mind that those time spans refer to telomere length, not overall aging.
"Our results emphasize the potential wide-ranging effects of the two most
important preventable exposures in developed countries -- cigarettes and
obesity," write the researchers.
They point out that there was "considerable variation" in telomere length
between participants and call for larger studies on the topic.
Possible Explanation
"Obesity and smoking are important risk factors for many age-related diseases.
Both are states of heightened oxidative stress . and inflammation," say the
researchers. That could wear down the white blood cells' telomeres, and bigger
studies should be done to check that, the study notes.
Other researchers have also suggested that telomere length indicates aging as
presented in a small study tied weight gain and insulin resistance to shortened
telomeres. weight gain and insulin resistance to shortened telomeres. That
report appeared in the journal Circulation.
Another study in the Proceedings of the National Academy of Sciences
showed a link between chronic stress and shorter telomeres. chronic stress and
shorter telomeres. A third study, published in The Lancet 's Feb. 1, 2003
issue, showed an association between shorter telomeres and greater risk of
death shorter telomeres and greater risk of death from heart disease and
infectious diseases.
By Miranda Hitti
Reviewed By Kathleen Zelman, MPH, RD, July 25, 2007.
Medically updated July 25, 2007.
SOURCES: Valdes, A. The Lancet , June 14, 2005; online
edition. WebMD Medical News: "Extra Weight May Age You Faster." WebMD Medical
News: "Chronic Stress May Make Cells Age Faster." WebMD Medical News: "Life
Span Lives in Length of Chromosomes." News release, The Lancet .
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