THERE is "no survival advantage" in being overweight or obese.

That might sound obvious, but in fact it runs contrary to a long-standing medical mystery which has stumped scientists and clinicians for years: that heavier people were less likely to be hospitalised or die than those of normal weight. 

Now scientists in Glasgow have found that measuring excess body fat based on the waist-to-height ratios - rather than body mass index BMI) is a more accurate predictor for future health problems.

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Their research debunks a phenomenon known as the "obesity paradox", whereby patients with heart failure who are overweight or obese appear statistically less likely to end up in hospital or die than people of normal weight.

READ MORE: Have we finally found a weight-loss drug that works? 

Previous analysis had found that while people who are overweight or obese are at higher risk of developing heart problems than those of a healthy weight (a BMI of 18.5 to 24.9), patients with higher BMIs were less likely to die once they had a heart condition than people of normal weight with the same diagnosis.

The counterintuitive findings have puzzled medics and scientists, with various theories put forward over the years.

These included a suggestion that some extra fat might be protective against further health problems and death, especially as people who develop a severe and chronic illness often lose weight.

Researchers and clinicians remained unconvinced, however.

HeraldScotland: The study was led by Professor John McMurrayThe study was led by Professor John McMurray (Image: Glasgow University)

Now Glasgow University researchers have shown that if doctors measure the waist to height ratio of their patients, instead of relying on BMI, the apparent survival advantage for people with a BMI of 25-plus disappears.

The findings are published today in the European Heart Journal.

The study analysed data from 1,832 women and 6,567 men with heart failure and what is known as "reduced ejection fraction" - where the amount of blood pumped by the heart per beat is lower than it should be.

The measure is commonly used by doctors to evaluate heart health.

READ MORE: Obesity, women and the surprising cost of 'being too fat'

Participants were drawn from an international randomised control trial, known as PARADIGM-HF, which is taking place in 47 countries worldwide.

Doctors collected data on BMI, blood pressure, body measurements, results from blood tests, medical histories and treatments.

Once analysed, the data on BMI and waist-to-height ratio showed that more body fat was associated with a greater risk of death or hospitalisation for heart failure. This was more evident for waist-to-height ratio.


When looking at waist-to-height ratio, the researchers also found the top 20 per cent of people with the most fat had a 39% increased risk of being hospitalised for heart failure, compared to people in the bottom 20% who had the least fat.

John McMurray, a professor of medical cardiology at Glasgow University who led the research, said: “Our study shows there is no ‘obesity survival paradox’ when we use better ways of measuring body fat.

"BMI does not take into account the location of fat in the body or its amount relative to muscle or the weight of the skeleton, which may differ according to sex, age and race.

"In heart failure specifically, retained fluid also contributes to body weight.

"Our study has clarified the true relationship between body fat and heart failure patient outcomes, showing that greater obesity is actually associated with worse not better outcomes, including high rates of hospitalisation and worse health-related quality of life.”

READ MORE: Male heart deaths in Scotland at highest number in a decade

Naveed Sattar, a professor of metabolic medicine at Glasgow University, said further trials are needed to determine whether weight loss can improve patients' outcomes.

He added: “In the UK, the National Institute for Health and Care Excellence (NICE) now recommends that waist-to-height ratio instead of BMI is used for the general population, and we should support this for patients with heart failure too.”