May 25, 2005 -- You probably already know that gaining weight isn't good for you. Now, a new study shows that extra pounds may literally make you old before your time.
The news, reported in Circulation earlier this month, doesn't center on gray hair or wrinkles. Instead, it delves down into the blood. White blood cells show telltale signs of aging when weight gain or insulin resistance is present, the study shows.
Insulin resistance means that the body's ability to control blood sugar is faltering. It can be a warning sign of looming health risks including diabetes and the metabolic syndrome, a group of abnormalities that raises the risk of heart disease.
The results came from the Bogalusa Heart Study, a long-term research project including black and white adults and children in and around Bogalusa, La. The researchers included Gerald Berenson, MD, who started the study in 1973 to track heart disease risk factors.
Back then, many participants were in grade school. Now, Berenson and colleagues studied them as adults.
The study included 49 black and white young men and women. All had their height, weight, and blood sugar (glucose) levels recorded at least twice between 1988 and 2001.
There was one more piece of key data: the length of their white blood cells' telomeres. Telomeres are part of the cells' chromosomes, which house DNA. Those telomeres naturally get shorter with age.
Shorter telomeres were associated with weight gain and insulin resistance, say researchers.
Telomere length and changes can vary between people and run in families, they note.
What made the telomeres shrink faster than normal? The study doesn't settle that, but cell-damaging free radicals and inflammation might be responsible, say the researchers.
For instance, they say that obesity is associated with increased inflammation because fat tissue is a major source of inflammatory chemicals. "Inflammation promotes an increase in white blood cell turnover, which would enhance telomere attrition," they write.
In other words, inflammation burns out white blood cells faster, and the effort of replacing them wears down the telomeres.
Insulin resistance and obesity are also associated with free radical damage, the study explains. Those damaged cells become "free radicals" that can hurt DNA in normal cells, laying the groundwork for health problems.