Low-fat diets could increase the risk of an early death, a major study has found.
A global study of 135,000 people reveals that people who eat the least fat have the highest mortality rates.
The findings, presented at the world’s largest heart conference, challenge decades of dietary advice which have focused on persuading people to cut fat.
The Canadian research team, who published their study in the respected Lancet medical journal, said fat may actually have a protective effect on human health.
They found people with the lowest fat intake were 23 per cent more likely to die young.
The scientists said people should instead cut back on carbohydrates – the potatoes, bread, pasta and rice which UK health authorities say should be at the centre of a healthy diet.
The findings, presented at the world’s largest heart conference, challenge decades of dietary advice which have focused on persuading people to cut fat
Experts said the new findings ‘add to the uncertainty about what constitutes a healthy diet’ – and said this confusion is likely to last for years to come.
The study immediately provoked a row between British health experts, many of whom stood by the conventional advice that people should cut their fat intake.
Challenging decades of dietary advice
But researcher Dr Mahshid Dehghan of McMaster University, speaking at the European Society of Cardiology congress in Barcelona, said: ‘For decades, dietary guidelines have focused on reducing total fat and saturated fatty acid.’
But she added: ‘The body needs fat. It carries vitamins, it provides essential acids, it has a role in the body.
‘When you reduce fat to very low levels, you’re affecting these important minerals.’
She stressed that people should not eat unlimited fat – and if people actually hit the British guidance of getting 35 per cent of energy from fat, they will give themselves the best health.
But she said the focus on ‘low-fat’ dieting – a drive supported by UK authorities – means people often go below this level.
And when people try to cut fat they replace it in the diet with carbohydrates and sugar, increasing their heart risk.
‘When you emphasise a diet that is low in fat people replace fat with carbohydrates,’ she said.
How was the study carried out?
Her team assessed the diets of 135,335 people, aged 35 to 70, from 18 countries in Europe, the Americas, Asia and Africa.
Over 7.4 years the researchers found that people who had the highest fifth levels of carbohydrate intake were 28 per cent more likely to die than those who had the lowest fifth.
And those who had the lowest fifth of total fat intake were 23 per cent more likely to die than those who had the highest fifth.
Dr Dehghan said: ‘Limiting total fat consumption is unlikely to improve health.
‘A high carbohydrate diet – greater than 60 per cent of energy – is associated with higher risk of mortality.
‘Higher intake of fats, including saturated fats, are associated with lower risk of mortality.’
Carbohydrates could be to blame
Fellow researcher Dr Andrew Mente said: ‘Every essential nutrient has a sweet spot where being in the middle is optimum. And there is no reason to believe that things are not different for different types of fats including saturated fat.
‘Our message is one of moderation. Our data suggests that low fat diets put populations at increased risk for cardiovascular disease.
‘Loosening the restriction on total fat and saturated fat and imposing limits on carbohydrates when high to reduce intake to moderate levels would be optimal.’
Public Health England recommend adults get up to 35 per cent of their energy intake from all types of fat and 50 per cent from carbohydrates, such as bread, pasta and sugar.
The scientists said people should instead cut back on carbohydrates – the potatoes, bread, pasta and rice which UK health authorities say should be at the centre of a healthy diet
It says no more than 11 per cent should come from saturated fat – found in cheese, butter and cream.
British cardiologist Dr Aseem Malhotra, who for years has fought against the advice that fat should be cut, said: ‘It’s time for a complete U-turn in the dietary guidance.
‘The sooner we do that the sooner we reverse the epidemic in obesity and diabetes and the sooner start improving health.’
Experts call for a reconsideration of guidelines
Professor Jeremy Pearson of the British Heart Foundation said the UK should now reconsider official dietary guidelines, particularly around carbohydrates.
For decades, dietary guidelines have focused on reducing total fat and saturated fatty acid
Dr Mahshid Dehghan of McMaster University
He said: ‘This study suggests we should perhaps pay more attention to the amount of carbohydrate in our diet than we have in the past and we may need to revise the guidelines.
‘What I don’t think people should do is get excited and think ‘I can eat as much saturated fat as I like’.
Years of confusion ahead
A Lancet editorial, written by scientists at the US National Institute on Aging, warned that years of confusion will follow the study.
‘These findings challenge conventional diet-disease tenets … adding to the uncertainty about what constitutes a healthy diet,’ it said.
‘This uncertainty is likely to prevail until well-designed randomised controlled trials are done.’
It added: ‘Until then, the best medicine for the nutrition field is a healthy dose of humility.’
But Professor Susan Jebb, the government’s former obesity tsar and an academic at Oxford University, called the findings into question, and said: ‘The background diet of most of the countries in this analysis is very different from the UK.
‘There are many other non-diet related factors which contribute to differences in ill-health and the causes of death.’