Overweight and obese people could slash their increased risk of heart disease by half and their increased risk of stroke by three quarters by controlling their blood pressure, cholesterol and blood sugar, a big new international study suggests.
The study, to be published Friday in the medical journal Lancet, is the largest so far to make the case that people who weigh too much can do themselves a lot of good by getting those risk factors under control through lifestyle changes and medication, even if they fail to lose weight. Blood pressure control appears especially important.
But they still will face higher risks than people with normal weights, says lead researcher Goodarz Danaei, an assistant professor of global health at the Harvard School of Public Health in Boston.
"The glass is kind of half empty and half full," he says. "You still need to control weight to get the full benefit."
The findings have meaning for a majority of adults in the USA: About two-thirds areoverweight or obese, according the federal Centers for Disease Control and Prevention. CDC also says one-third of all adults have high blood pressure and half do not have it under control.
For the study, researchers from Harvard, the Imperial College London and the University of Sydney pooled data on 1.8 million people who participated in 97 studies around the world. The researchers compared normal-weight people with otherwise similar people of the same age and sex who were overweight or obese, as defined by BMI (body mass index) a measure of weight relative to height.
The studies all followed people over a number of years. As expected, overweight and obese people had more strokes and heart disease and were more likely to have high blood pressure and unhealthy cholesterol and blood glucose numbers. The aim of the study was to look at how much of the increased heart and stroke risk was explained by those risk factors — rather than something else about being overweight or obese. Among the findings:
• 76% of the extra risk for stroke and 46% of the extra risk for heart disease was explained by the three risk factors.
• 65% of the extra stroke risk and 31% of the extra heart disease risk was explained by high blood pressure alone.
• Cholesterol and blood glucose levels had a smaller, but still significant, impact.
• The absence of risk factors seemed to matter less for the heaviest participants — meaning that other still poorly understood health changes associated with obesity may put them at higher risk for heart disease and stroke.
The study has some limitations, including the fact that the smaller studies it included often lacked information on exercise and diet, Danaei says. But, "the sheer size of the study reduces the uncertainty." It's also striking, he says, that researchers found the same risk patterns in rich and poor countries, in the West and in Asia.
It's an "excellent study," and in line with most previous reports, says Carlos Lorenzo, a researcher at the University of Texas Health Science Center at San Antonio who was not involved in the study. But, he says, more research is needed on other factors, such as inflammation and nervous system changes, that might accompany obesity and contribute to health risks. "There's continuing controversy over whether obesity itself is a risk factor," he says.
The dual message that people should control weight and cardiovascular risk factors is a good one, says Adam Tsai, an internist at the University of Colorado-Denver who specializes in obesity treatment and is a spokesman for the Obesity Society. He says it may be easier for many people "to take medication every day to lower blood pressure than to lose weight and keep it off."
But, he says, patients also should know they stand to gain many other health benefits from losing weight. Obesity increases risks for diabetes and certain cancers, as well as conditions ranging from sleep apnea to osteoarthritis, according to the CDC.
New guidelines for physicians, just released by the Obesity Society, American Heart Association and American College of Cardiology, urge them to treat obesity just as aggressively as any other ailment.
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