Too much body fat in middle age increases hardening of arteries, according to a new study by researchers at Imperial College London.
The study looked at 200 volunteers aged from 18 to 80 and found that arteries progressively stiffened as the percentage of fat in a person over 50 increased, potentially increasing their risk of suffering heart disease or a stroke.
When you are younger, blood vessels are able to counter this effect, the researchers say, but this does not continue into older age.
Declan O'Regan, who led the study, said: “Previous studies of young people and children suggest they are better able to adapt to excess body fat. But as you get older these mechanisms do not work as well. There is good evidence that metabolic products that circulate through the blood damage the elasticity of fibres so after a period of time they stiffen.
"Other studies have looked at specific age ranges – for example young people or elderly people. Our study looked at a wider range. There are still a lot of unknown mechanisms at play. What we do know is that the older you are and the more body fat you have quite clearly has a worsening effect on your arteries.”
Researchers measured the speed of blood flow through the aorta, the body’s biggest artery. A hardening of the aorta means blood flows faster through it than in healthier, more elastic ones.
Although the research, which was published in the journal Hypertension did not specify where exactly the damage might be irreversible, O'Regan said that the benefits of losing weight to cut down on the risk of developing health problems could depend on what age you are and how long you have been overweight.
“Our research suggests there may be a link,” he said. “We’ll look into whether losing weight to cut down the risk of stroke or heart disease is more effective for some age groups, for example if you are in your 40s, and whether how long you have been obese makes a difference.”
While the links between obesity and heart disease is well known, the reason for this is less fully understood.
A report into obesity in England found that in 2011, 24.8% of adults (aged over 16) and 16.3% of children were obese.
A common way of measuring obesity is by using BMI but Imperial researchers calculated the percentage of fat of volunteers by passing a small electrical current through the body.
G. Neil Thomas, from the University of Birmingham’s School of Health and Population Sciences, said BMI wasn’t an accurate measure for obesity in many cases.
“If you look at BMI on an individual basis, someone like Arnold Schwarzenegger when he won Mr Universe would have been classified as obese, which is clearly not the case,” he said. “There is a subset of people for whom it does not measure risk accurately. But if you look at the central obesity measures, such as waist circumference, you can more accurately tell who would be metabolically at risk.”
“As you increase your adiposity [the amount of fat that you have], other factors worsen along with it – for example blood pressure. The good cholesterol goes down, inflammation and your risk of diabetes goes up, along with many other underlying factors.”
In March, a study by researchers at University College London (UCL) of more than 4,000 people found that obese people who suffered from heart disease were less likely to die early than those who were of normal weight. Researchers called this the obesity paradox.
UCL researchers said doctors may treat the disease more aggressively in obese people and the British Heart Foundation added that how people stored fat, not just general obesity, was important.