Many Americans aim to eat low-fat foods but there is strong evidence that replacing fat with carbohydrates could be harmful to health, according to nutrition experts at the ADA conference in Boston last week.
Recommendations to reduce saturated fat intake are largely based on the notion that high levels increase risk of cardiovascular disease, but unless saturated fat is replaced with other fats, many studies have suggested that fat reduction could increase risk of heart disease.
During a symposium called “The Great Fat Debate: Is There Validity In the Age-Old Dietary Guidance?” at the American Dietetic Association’s (ADA) Food and Nutrition Conference and Expo, four leading experts presented evidence suggesting that low fat diets may be less healthy than those containing at least a moderate amount of fat. In particular, all four agreed that replacing saturated fat with carbohydrates – as has been widely recommended in the United States – is likely to raise the risk of cardiovascular disease.
The low fat message
Director of the cardiovascular health laboratory at Tufts University Dr. Alice Lichtenstein said dietary advice to adhere to a low fat diet is based on an oversimplification of recommendations.
“The emphasis should be on displacing saturated fat and trans fat with unsaturated fat because that is where the data is,” she said. “…‘Displace saturated fat with polyunsaturated fat’ was simplified to ‘low fat’. Then ‘low fat’ became ‘low calorie’. The low fat message is still very pervasive, especially in the lay press.”
Chair of the Harvard School of Public Health’s nutrition department Dr. Walter Willett takes this even further.
“If anything, the literature shows a slight advantage of the high fat diet,” he said. “The focus on fat in dietary guidelines has been a massive distraction…We should remove total fat from nutrition facts panels on the back of packs.”
He added that while the pervasive dietary guidance given to consumers has been to eat fats sparingly, to load up on starch and eat non-fat products, “the food industry quickly realized sugar was cheaper than fat and laughed all the way to the bank.”
“It was really the type of fat that was important,” he said. “If you replaced saturated fat with polyunsaturated fat there was a reduction of risk.”
American eating behavior
Meanwhile, distinguished professor of public health and professor of epidemiology at the University of Pittsburgh’s Graduate School of Public Health, Dr. Lewis Kuller, said that dietary guidance to reduce saturated fat should not change, considering that too much of the fat in the American diet is saturated and not enough is unsaturated.
“The biggest problem in America at the moment is eating behavior,” he said. “…Eating is a social pleasure and not a therapeutic challenge. We have done a great job of confusing the public.”
The importance of overall diet
Assistant professor of medicine at Harvard Medical School Dr. Mozaffarian agreed with the other speakers about a lack of evidence linking total fat consumption and cardiovascular disease risk.
High levels of low density lipoprotein (LDL cholesterol) and high triglyceride levels have both been linked to increased risk of cardiovascular disease, but Mozaffarian said there has often been overreliance on single biomarkers in drawing conclusions about fats’ impact on heart health, “even one as hallowed as LDL cholesterol”.
“Overall dietary quality is very important for cardiovascular risk,” he said. “Saturated fats may raise LDL cholesterol but increasing levels of all fats lowers triglycerides…You can’t look at data across countries and draw conclusions. Nor can you look at animal studies or a single biomarker and draw conclusions from that.”
Concluding the discussion, Dr. Lichtenstein warned against focusing on single nutrients for disease risk reduction.
She said: “We need to stop focusing on individual dietary components because when one goes down, another goes up.”