Study challenges 'obesity paradox'

The idea that it might be possible to be overweight or obese, but not at increased risk of heart disease, has been challenged by a new study.

Researchers said their findings dispute the "obesity paradox" that being overweight or even obese might not have any effect on the risk of death from cardiovascular disease (CVD) or other causes, and may even be protective, especially if people maintain a reasonable level of fitness.

Their study, which analysed the data of nearly 300,000 people, found the risk of heart and blood vessel problems - such as heart attacks, stroke and high blood pressure - increases as body mass index (BMI) rises beyond 22-23, even though a BMI of between 18.5-25 is usually considered healthy.

Furthermore, the risk also increases steadily the more fat a person carries around their waist.

The research, carried out by the University of Glasgow, found that people with a BMI between 22-23 had the lowest risk of CVD.

Above that level, the risk of CVD increased by 13% for every 5.2 increase in women and 4.3 in men.

Compared to women and men with waist circumferences of 74cm and 83cm respectively, the CVD risk increased by 16% in women and 10% in men for every 12.6cm and 11.4cm increase respectively.

Similar rises in CVD risk were seen when the researchers looked at waist-to-hip and waist-to-height ratios and percentage body fat mass - all of which are considered reliable ways to accurately gauge the amount of fat a person carries, also known as adiposity.

Lead researcher Dr Stamatina Iliodromiti said: "Any public misconception of a potential 'protective' effect of fat on heart and stroke risks should be challenged.

"This is the largest study that provides evidence against the obesity paradox in healthy people.

"By maintaining a healthy BMI of around 22-23 kg/m2, healthy people can minimise their risk of developing or dying from heart disease. In terms of other adiposity measures, the less fat, especially around their abdomen, they have, the lower the risk of future heart disease."

She said it is possible it may be different for those with pre-existing disease, as there is evidence that in cancer patients, for instance, being slightly overweight is associated with lower risk, especially as cancer and its treatments can lead to unhealthy weight loss.

The team said they also recognise it can be difficult for some people to maintain a low BMI, particularly as they get older.

Study co-author, Professor Naveed Sattar, said: "We know many cannot get to such low BMIs so the message is, whatever your BMI, especially when in the overweight or obese range, losing a few kilograms or more if possible, will only improve your health.

"There are no downsides to losing weight intentionally and the health professions needs to get better at helping people lose weight."

Researchers said their findings may have implications for guidelines on preventing and managing cardiovascular disease.

Dr Iliodromiti added: "Even within the normal BMI category of between 18.5-25 kg/m2, the risk of CVD increases beyond a BMI of 22-23 kg/m2.

"The other adiposity measures show that the leaner the person the lower the risk of CVD, and this must be a public message, that healthy individuals should maintain a lean physique to minimise their risk of CVD."

The study, which is published in in the European Heart Journal, involved the data of 296,535 adults of white European descent who are taking part in the UK Biobank study, and who were healthy at the time of enrolment between 2006 and 2010.