Being "fat but fit" is a myth with those carrying excess weight at almost double the risk of heart failure, a new study suggests.

Research into the medical records of 3.5 million Britons has led experts to conclude there is no such thing as being "healthily obese".

Debate has raged over whether those who carry extra fat, but have normal blood pressure and cholesterol levels and do not suffer from diabetes - known as being metabolically healthy - can truly be considered to be in good health.

Previous studies had claimed up to one in three obese people are healthy.

But, by studying millions of medical records from 1995 to 2015, a University of Birmingham team found those who were obese but regarded as metabolically healthy still had almost double (96%) the risk of heart failure.


Compared to healthy people not carrying extra weight, those who were obese also had a 49% increased risk of coronary heart disease and a 7% greater risk of suffering a stroke.

The findings held true also when factors such as smoking were taken into account.

Healthy overweight people who had never smoked were still found to be at an increased risk of peripheral vascular disease.

People are classed as obese if their body mass index (BMI) is 30 or more.

Critics have claimed it is a crude way to determine obesity as athletes with dense muscle mass can sometimes have the same BMI as someone carrying lots of excess fat.

Image: People are classed as obese if their body mass index (BMI) is 30 or more

The study's lead author Dr Rishi Caleyachetty said the research revealed "the idea of being healthily obese is a myth" and that being metabolically healthy "is not a harmless condition".

"It's actually better not to use this term as it can create a lot of confusion," he added.

Dr Mike Knapton, associate medical director at the British Heart Foundation, said: "It's not often that research on this scale and magnitude is able to clarify an age-old myth.

"These findings should be taken extremely seriously and I'd urge healthcare professionals to take heed."

But Tam Fry, chairman of the National Obesity Forum, claimed the research ignored other recent studies suggesting there is a genetic explanation for why some people can carry extra fat but appear not to suffer ill health.

He said: "Can you be fat and fit? Ask any group of rugby forwards who shift their bulk up and down a 100m field for 80 minutes and you'll get a 'yes'.

"Ask scientists stuck in a lab and you might not.

"Unfortunately, the Birmingham researchers appear not to have factored in recent genetic evidence that goes a long way to explaining why so many fat people appear not to suffer ill health.

"These people have the ability to store large amounts of fat around their bodies yet remain fit. And so the debate rages on."