This sounds very logical to me. If you smoke or are obese you are most likely biologically older than other slim non-smoking individuals, because we all know that obesity and smoking are important risk factors for many age-related diseases.

Tim Spector (St. Thomas' Hospital, UK) and colleagues in the USA looked for evidence of ageing at a molecular level in smokers and obese individuals.

US and UK scientists looked for evidence of ageing at a molecular level in smokers and obese individuals and analyzed telomeres, which cap the ends of the chromosomes in our cells and protect them from damage. Every time a cell divides, and as people age, their telomeres get shorter.

This study has been made in UK where were recruited over a thousand women aged from 18 up to 76 years old. 12% of the women were obese with BMI greater then 30. Only 8% of tested women had a BMI under 20! 52% of them never smoked, 32% were ex-smokers and 16% were current smokers.

The investigators measured the concentrations of a body fat regulator called leptin and telomere length in blood samples from the women. They found that telomere length decreased steadily with age and the telomeres of obese women and smokers were much shorter that those of lean women and never-smokers.

Lean individuals had significantly longer telomeres than women with midrange BMIs, who, in turn, had longer telomeres than obese individuals. Each pack-year smoked was equivalent to a loss of an additional 18% on top of the average annual shortening of telomeres.

Final statement after this study is that obesity and cigarette smoking accelerate human ageing! “Our results emphasizes the potential wide-ranging effects of the two most important preventable exposures in developed countries- cigarettes and obesity.” said Professor Tim D Spector, Twin Research Unit from London’s St Thomas' Hospital.

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