Obesity Increases Damaging
'Free Radical' Particles

NEW YORK (Reuters Health) - People who are obese seem to have higher-than-normal levels of oxidative stress, an accumulation of the cell-damaging substances called "free radicals," according to a new study.

This may be one reason why those who are overweight are at greater risk for developing heart disease.

"Obesity, which has always been considered a risk factor for heart disease and diabetes, really looks like it's related to oxidative stress, and that may be one of the reasons as to why obesity is bad for a person," lead author Dr. John F. Keaney Jr. told Reuters Health.

Oxidative stress, which is believed to contribute to a number of different diseases and the aging process, is a normal byproduct of body processes.

But Keaney cautioned that it is too soon to conclude that obese people should take antioxidant vitamins, which counteract free radicals.

"You can't use the study to say that people should take antioxidants," said Keaney, who is at Boston University School of Medicine in Massachusetts. "You have to take it at face value and realize that more research will need to be conducted to learn more about the relationship."

Nonetheless, Keaney added that the study "clearly shows that obesity is associated with elevated levels of" chemicals that are markers for oxidative stress.

Scientists have long sought to learn more about oxidative stress, but assessing oxidative stress chemicals in the body has been difficult. Now, a new method allows researchers to measure levels of an oxidative stress-related chemical in the body called 8-epi-PGF (2-alpha).

The new method now makes it possible to assess the relationship between oxidative stress and a number of conditions, including hardening of the arteries, high blood pressure and diabetes, according to a report published in Arteriosclerosis, Thrombosis and Vascular Biology: Journal of the American Heart Association.

In the study, the team of researchers wanted to understand how much oxidative stress contributes to heart disease, Keaney explained in an interview with Reuters Health.

Keaney's group tested urine samples of 2,828 men and women for the presence of 8-epi-PGF (2-alpha), which indicates the degree of oxidative stress in the body.

Previously, it was widely believed that high cholesterol and high blood pressure were strongly associated with oxidative stress. That was not supported by the present study, Keaney said.

However, smoking and diabetes were related to higher levels of oxidative stress. But "the big finding that nobody predicted is that body mass index (a measurement which indicates obesity) is a marker for oxidative stress," noted Keaney.

In general, the higher a person's body mass index, the higher were their levels of 8-epi-PGF (2-alpha) and therefore the more oxidative stress present in their body.

"Obesity is the predictor of oxidative stress, independent of other stuff," said Keaney.

Still, Keaney pointed out that it remains to be seen how detrimental high levels of oxidative stress are.

"We will have to wait until we see what happens to these people with the higher levels of oxidative stress," he said. "We want to see if they have higher rates of heart attack and death compared to people with lower oxidative stress levels."

However, Keaney also noted that there is a growing body of literature that suggests that the more oxidative stress people have, the more likely they are to have blood-vessel disease.

Oxidative stress, then, may be the "connector between obesity and other disease," said Keaney. "We cannot prove that from this study, the study just raises that possibility and provides reasons for further investigation."

SOURCE: Arteriosclerosis, Thrombosis and Vascular Biology 2003;23:434-493.

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